Rachel Zoe greets me at the door of her New York hotel room with her head tilted to one side and a large brush entrenched in her beachy-blonde wet hair. Her bathrobe is about 12 sizes too big for her. 'Oh my God,' she says, 'today has been...' She glances round at the Blackberry on the bed and lets her arms slump to her sides in defeat. 'I just got 45 emails in the last three minutes.' The phone rings. 'Hello-oh?' she sings, 'Grand Central?'
As anyone in the fashion industry will concede, Rachel Zoe (whose surname rhymes with 'low') is one of the most influential people in the business. The most sought-after celebrity stylist of the moment, she has minted a certain young Hollywood look: tousled hair, perpetual tan, smoky eyeshadow, oversized sunglasses, layers of gold jewellery, huge handbags, vintage jersey dresses - an overly svelte Studio 54-meets-Saint Tropez boho chic. Lindsay Lohan, Nicole Richie and Mischa Barton - actresses revered in the style pages of Heat, Grazia and the fashion press, and as Zoe calls them, 'my girls' - are styled by her, are friends of hers and look exactly like her.
When it comes to the Oscars and other red-carpet events, she styles Kate Beckinsale, Jennifer Garner, Anne Hathaway and Keira Knightley (whose Vera Wang gown - co-designed by Zoe - was widely voted best dress of the night this year). So Zoe is widely worshipped.
'When a celebrity wears a certain designer,' Zoe explains to me later, 'it's at least a year of free advertising.' She won't reveal her fee, but it's rumoured to be around $6,000 a day.
Yet Zoe's influence is felt far beyond the fashion industry. By altering a client's look, she can change their fame and fortune - in that respect, Zoe is more Louis B Mayer than Coco Chanel. Not so long ago, Lohan and Richie were teenage laughing stocks; now they are among the most photographed stars in Hollywood.
'Those girls get photographed going to dinner. They get photographed going to lunch. They get photographed from the minute they leave their houses in the morning till the minute they go to sleep,' Zoe says - and every one of those minutes has been styled by her.
Due to the dramatically reduced frames of her young friends Mary-Kate Olsen and Nicole Richie, Zoe was recently credited with 'single-handedly bringing anorexia back into fashion', a contentious comment that, though uncharitable in intention, implies an enormous degree of influence: it's not just about sunglasses - Rachel Zoe can shift the popularity of an entire psychiatric condition.
'For Rachel, life is a fashion shoot,' says Harper's Bazaar editor Glenda Bailey, who noticed one season last year that Zoe's look had influenced all the catwalk shows. 'People underestimate her power,' agrees Zoe's friend Nicole Garcia, American Elle's fashion director. Where once magazines set the trends, now they take their cues from the celebrities they feature instead of models on their covers.
Paul Cavaco, creative director of Allure magazine, says, 'We can be snobbish about "high fashion" but, in fact, what people are looking at is Hollywood. And Rachel's dressing all those young Hollywood starlets.' Zoe's friend Michael Kors agrees. 'It's not just the red carpet,' says the designer. 'We've never lived in such a paparazzi moment. So many women get their fashion information by looking at a tabloid, and she has found a way of making those girls look intriguing and fabulous when they're running out for a Starbucks'.
She's very influential - she has editorial pages running all over the world without editing a magazine.' Zoe was spending the week in New York, and I wanted to know what a week in her life was like. When I'd phoned to ask if I could shadow her she'd laughed. 'Fasten your seat belt. It's a roller-coaster ride.'
On Monday night, she was due to go to the Council of Fashion Designers of America Awards (CFDA) - a big day in the fashion calendar. On Tuesday there was a photo shoot with Lohan for UK style magazine i-D. On Wednesday there was a Missoni event, on Thursday it was Cartier. Oh my God, she thought out loud, looking at her crazy schedule - did I want to come and talk to her while she had her hair and make-up done?
So here I am in her hotel room, squeezed between makeup artist and hairdresser. 'Last night, someone asked me who did my nose,' Zoe is telling the assembled audience. 'I was like: "Oh my God - my mother! I was born with this nose!"' (Despite having moved to LA three years ago, Zoe is militantly anti-plastic.)
'So,' asks the hairdresser from behind, 'are we gonna do like, more of a loose wave?'
'Yeah, I think a wave. I mean, you could do... Think Giselle. Giselle hair.'
Zoe turns to me and adds: 'And I love Giselle personally. She's so kind, and so modest... The first thing she always says is, "Oh my God, Rachel you look so beautiful!" I really think supermodels say that to civilians just to make them feel better about themselves. But it's OK. I got over it a long time ago.'
Zoe is 34. She says she feels like a grandmother sometimes, hanging out with all these teenage starlets. At other times she thinks it keeps her young. Either way, age has given her a degree of cool, both in temperament and style, which her diva friends lack. By all accounts one of the few down-to-earth people in a world of hyper-inflated egos, Zoe has fox-coloured eyes and looks roughly as Brigitte Bardot would have, had she coincided with the era of Halston. She is warm, bright, sisterly and has, since girlhood, been utterly possessed by a love of glamour.
She was born Rachel Zoe Rosenzweig in New York and grew up in Short Hills, New Jersey, the daughter of wealthy art collectors. As a child, she was surrounded by Frank Stellas, Keith Harings, Barbara Krugers, 'all that stuff' - and by vintage Chanel, vintage Lanvin, vintage Dior. Zoe likes to say she was born into her mother's closet. 'It was like a candy store when I was a kid,' she tells me, 'I used to go in there and put everything on at once. You know, more is more is more is more - that's my motto. And I stole it all!'
She studied sociology and psychology at university - skills she has said that come in handy in Hollywood - and met her future husband Roger Berman there 15 years ago. Once an investment banker, Berman now has a business of his own - he buys award shows - which allows him to travel with her. 'I'm telling you, I am nothing without him,' she says. 'He keeps me sane.'
Berman has, however, threatened to walk out temporarily around Oscar time next year. From the moment nominations are announced to the second a star hits the red carpet is, for Zoe, 'colossal mayhem. It's one of those things where it used to be my favourite time of year,' she says, 'but I think that the competition has got so fierce among designers...'
Substantial bribes have been offered; she never takes them. 'Some people you think are really your friends,' she muses. 'When it gets to the nitty-gritty and they're desperate to get that placement you see, like, the dark side.'
The phone rings. It's Louis Vuitton. Can they send some stuff over? I ask Zoe what is the most brutal piece of advice she's ever given a client. 'I never give brutal advice,' she says. 'Probably the most brutal is how to stand. How to work a dress. But I would never in a million years tell a client they had to lose weight,' she adds. 'Ever. And it's not my place. I wouldn't even tell my best friend that. There's a size for everybody.'
Of course, Zoe knows that she is expected to dispel the rumours that she has fostered anorexia.
'I think an eating disorder is a very sad thing, a very serious thing - it kills people,' she says emphatically, and quickly undercuts that by adding: 'People don't realise that I've worked with people who are size eight, and 10,' (this, dear reader, is meant to stand for 'extremely large'). 'I don't think it's fair to say that I'm responsible because I'm a thin person, that because I'm influencing their style I influence what they eat. And then there was this crazy rumour that I was getting diet pills from Mexico and, like, distributing them. I was like, "OK, I've never even tried cocaine. I don't do drugs - I'm too much of a control freak."
The phone rings again. It's someone inviting her to P Diddy's after party tonight. 'Yeah,' she says, 'I'll totally come by.' I ask Zoe if she believes she can change a person's status if they have a bad reputation - for drugs, drink, poor career choices? 'I don't know,' she replies. 'People say that I do.' Could she make anyone famous? 'No!' she laughs. 'You're giving me too much credit!'
Fifteen minutes to go before her car arrives. Her hair and make-up are perfect. The men leave and Zoe tips out a pile of accessories on to the bed. She's going to wear a vintage Chloe sheath, and is trying to work out which earrings go with it. She chooses several of her gold snakes and some oversized glass pendants, puts on the dress, walks out of the door, and decides something's not right. The belt hangs a little oddly. With the car waiting downstairs, she lets herself back in, switches all the jewellery, swaps her handbag and changes into a layered white vintage Halston.
Tuesday: a photography studio in the meatpacking district. Prince's greatest hits are blaring from the loud speakers, and at least half a dozen people are waiting for Lindsay Lohan to arrive. She is supposed to be shooting a cover for Cosmopolitan with her 12-year-old sister Ali, and then she is due to do a shoot for i-D.
Zoe wasn't supposed to be at the Cosmo shoot - she is only styling the i-D story - but I later learn that she was roped into coming because it was going to be difficult to get Lohan there at all otherwise. As it was, she was two-and-a-half hours late. They arrive, in identical false lashes, with identical tans, wearing each other's clothes. ('Lindsay borrowed my vintage Chanel handbag so I took her Hermes jacket,' Zoe says.)
Lohan is smoky-voiced and sore-stomached. From time to time there is talk of a doctor coming to the set to give her an injection. 'Last night was great,' she says of the CFDA awards, where she was Karl Lagerfeld's designated muse. 'Just being up there with Karl. We didn't leave each other's side. We were glued.'
As she has her make-up done, Lohan is given a sheaf of press clippings by her publicist. Zoe looks over her shoulder congratulating her as she flicks through photos of herself. They go over some options for the shoot - a beaded cream chiffon Temperley dress, a sequined Burberry shift, a Chanel two-piece with leather shorts. ('That looks so good - you have to wear that in real life,' Zoe tells Lohan, begging the inevitable question of when real life might begin.)
Then Zoe glances down at her Blackberry. 'Oh great,' she sighs, 'I just found out I have to go to a black-tie dinner tonight with her for Gucci. Tomorrow night's Missoni. Thursday night's Cartier. Oh my God, I'm gonna vomit!'
'Come on,' I say, 'it doesn't sound that bad.'
'Dude!' she replies, 'I got 15 years on this girl - everybody forgets that!'
She rushes off to button a dress. Later, Lohan returns from the bathroom, babbling excitedly about how someone in a neighbouring cubicle opened the door and nearly broke her nose. 'Oh my God,' she says, 'if she had been this much closer, I'd be at the plastic surgeon's by now.' 'That would be such a shame, Linds,' says Zoe distractedly, 'you have a great nose.' Her tone is perfect - supportive but not overindulgent, maternal but girlie, in charge but not overbearing. I don't know what I'd imagined Zoe to be like at work - something ditzier, perhaps, or, on the other hand, more grand. A back-seat Paris Hilton, a blonde Diana Vreeland - but her skills as an older sister should not be overlooked.
'We love her,' says Lohan's mother of Zoe during a break in shooting. 'She's so talented. And a good soul - very maternal. If Lindsay's in LA I don't worry because I know Rachel's there.'
Zoe's sister calls - a rare moment when she gets to speak to her ('My whole family emails me now to get in touch with me. I mean, imagine the Jewish guilt in my family - you have no idea.') The occasion for the call is crucial: Zoe's six-year-old niece wants to know if she can wear her jeans really long, with heels.
'Pamela,' says Zoe, 'I think you gave birth to my daughter, not yours.'
Meanwhile, the surreal mayhem of the day unfurls. There is a brief, fraught exchange relating to the shoot for i-D, which is famous for its winking cover stars. Matt Jones, the photographer - whose father, Terry, founded i-D - is concerned that Lohan's false lashes will interfere with the wink. 'I'm not taking my lashes off!' Lohan exclaims, before going into a brief but impressively energetic huff. She says Kate Moss doesn't jump - 'and I,' she adds flatly, 'don't wink. I don't wink!' Jones turns to me. 'In your piece, if my name is mentioned, could the word "patient" be next to it?'
A moment later, the make-up artist glances at some shiny black heels Lohan is trying on. 'Oh my God,' he says, 'I just bought some of those for my poodle!'
They missed the Gucci dinner that night - the shoot went on past 10:30pm - so they went to Da Silvano's for something to eat instead. The paparazzi swarmed around Lohan instantly.
If Zoe is used to dealing with her clients' fame, it is something of a discomfort to her to have to deal with her own. In the past few months, Zoe herself has been featured in Elle - showing readers her Missoni-bedecked home in Beverly Hills - and in Vogue, where we learned that she owns 400 coats. (Zoe's response, when I asked her how many clothes she had, was a near-heart attack: 'How many clothes? Oh God. I couldn't answer that question.')
Her friend Nina Garcia, fashion director of American Elle, tells me: 'I was with her at the CFDA Awards, when people were clamouring: "Rachel, Rachel, give me your autograph!"'
'It was surreal,' Zoe explains later on the phone. 'I walk outside, and there's a swarm of people screaming my name. I turn around, a n d t h e y ' r e l i k e , "Can we hug you? Can we kiss you? Can we have your autograph?" I signed, like, 30 autographs.'
I ask Paul Cavaco what happens when the celebrity stylist becomes as famous as the celebrities she styles. 'I don't know,' he replies slowly, 'it's never really happened before.'
Clearly, this is Rachel Zoe's 'moment'. But since she has such a recognisable style, will that not at some point go out of fashion? And when it does, will she be out of work? 'I'm always gonna wear my jersey Halstons and vintage YSLs and vintage Chanel jackets,' Zoe says. 'I've been wearing big sunglasses forever.'
As for her clients, she says, that's another story - 'You have to keep it new and interesting all the time.' And, as Cavaco points out, 'There's always someone you gotta fix.'
We meet again towards the end of the week, at the showroom of two ultra-glamorous young British designers, Keren Craig and Georgina Chapman, who operate under the name Marchesa. Zoe is a great supporter of theirs, and styled their last show. Though they have not been in business long, all of Zoe's 'girls' have already worn Marchesa dresses on the red carpet - the effect of which, they tell me, is extraordinary.
Today, Zoe is looking for dresses for Keira Knightley's Pirates of the Caribbean 3 premiere - and other dresses generally: she looks out for feminine things for Mischa, more edgy things for Lindsay, black or white things for Kate Beckinsale.
There are beautiful chiffon pieces draped and pinned on mannequins, and drawings on a board. White crepe silk palazzo pants are topped with incredible beaded embroidery. Craig designs the luscious textiles, and Chapman has been known to sculpt a piece of silk into a dress two hours before a show. They chat and giggle, and show me an entirely handmade red brocade dress from their archive - worn by Renee Zellweger to the premiere of the Bridget Jones sequel.
Zoe has had an amazing week. The Missoni event was 'fabulous', the Cartier party was 'incredible'. 'They did this dinner on the roof of the Cartier mansion - the first time they ever did anything like that in like 98 years,' she says as we leave the Marchesa showroom and try to find a cab back to her hotel. 'I got these charity bracelets: all these celebrities like Salma Hayek and Liv Tyler chose a bracelet colour for their charity - I bought four of them. There are so many different charities - I got a black, a red... anyway, the turnout was incredible - it was Sarah Jessica and Liv and Salma, and Cyndi Lauper sang.
And I am a die-hard Cartier girl. It's almost dangerous. No, it's not almost dangerous - it is dangerous. Oh my God, these YSLs are crippling me.'
Zoe never wears heels under five inches. If we don't find a cab soon her feet will be mangled.
'I 'd kill for my Louboutin espadrilles right now!' she sighs. Part of Zoe's appeal is that she lives the life of a movie star herself. She always spends Christmas in St Barth's and she summers, when she can find the time, in St Tropez. Every year, she gives her husband a Cartier watch. Her luggage, I am told, is to die for. But she also knows where her priorities lie. She loves 'the adrenalin rush of making someone beautiful'; at some point soon, though, she would like to chill out, maybe in a beach house in Malibu, maybe have a baby, work a little less to other people's schedules. Because after a while, the 'high school pettiness' of the celebrity styling world can get to you.
'Oh my God,' she laughs as a taxi pulls up, 'you have no idea. It's like, we're not saving lives here, we're dressing people: you've gotta get over it. It's not that deep.'