Sat by a pool in the shade of a lemon tree, celebrity make-up artist Julianne Kaye is pondering an eternal truth that underpins her glamorous profession. "In Hollywood, people change," she explains, chuffing sagely on a Marlboro Light. "In this town, a girl can go from zero to bitch in exactly six months."
Half a year, in Kaye's considered view, is roughly the length of time it takes for your average, fresh-faced new actress-singer-whatever to turn into a full-blown celebrity nightmare, complete with parasitic associates, destructive drug habits, eating disorders, small dogs, and all the other unwelcome accoutrements of overnight superstardom.
In the era of Paris Hilton and Lindsay Lohan, this may not sound like such a revolutionary hypothesis; but coming from Kaye, it is intriguing. She did, after all, spend much of the late 1990s looking after powder puffs, false lashes and lipgloss for the greatest celebrity train wreck of modern times: Miss Britney Spears.
Later, in a 14-year career that has seen her share confidences with some of Hollywood's biggest names, she went on to primp and preen the likes of Scarlett Johansson, Justin Timberlake and Eva Mendes. And this week, she will launch a novel loosely based on the experience. Its title is Pop Tart.
Co-written by Kira Coplin, a former red-carpet reporter for US Weekly, the book is pitched squarely at the chick-lit market, and its marketing literature has made uncomfortable reading in the entertainment companies based a stone's throw from Kaye's Sherman Oaks home.
Pop Tart is billed as a showbusiness version of The Devil Wears Prada. The books share an editor: Maxine Hitchcock at HarperCollins. But where its predecessor was a thinly-veiled expose of life in the office of Vogue editor Anna Wintour, Kaye's book aims to perform a similar "number" on Britney Spears.
It revolves around a make-up artist called Jackie, hired to work with the fictional Brooke Parker, an innocent blonde teenager with a Deep South accent who becomes a pop sensation thanks to a raunchy video and an ill-fated romance with a hot boy-band member.
Pretty soon, Parker starts smoking, drinking, and snorting her way around the Hollywood party circuit. Then she develops an eating disorder, sleeps around, gets a permanent paparazzi detail, and suffers a public disintegration, culminating in a nervous breakdown. It's interesting to wonder which scenes are hewn from the author's experience. There are intriguing accounts of cocaine-powered parties in Malibu, and 24-hour benders in Las Vegas, plus extraordinary displays of bitchiness and greed.
In real life, Kaye worked with Spears – who begins her UK tour tonight – well before the turbulent events of 2007 and 2008. But she witnessed come colourful behaviour.
"One thing I'll always remember was that I had to take her to my dad, who runs a salon, to fix her hair, because she'd dyed it purple in Colorado," she recalls. "She came into his salon in a wig, pulled it back, and said 'I need help.' "
Although HarperCollins is describing Pop Tart as a roman à clef and heavily touting its author's connection to Spears, Kaye officially describes Brooke Parker as an "amalgamation" of people ("the Lindsay Lohans of this world") and insists her book is unlikely to be seen as a betrayal. "This is fiction. I told everybody I've worked with and am still friends with about the book to feel them out. Even the people we were worried about were great about it."
One who may have performed a double take when she heard about the book is Scarlett Johansson, who, like Spears, found fame at an early age and worked with Kaye at the start of her career.
"I met Scarlett on My Brother the Pig, a movie she made when she was 16," recalls Kaye. "She stayed at my house for a week. One night, I put a bindi on her head and we went to a club, and [comic actor] Andy Dick cornered her. I was like, 'get away from her, she's a child'."
Another former acquaintance was Kaye's high-school contemporary Angelina Jolie: "She was a loner. She wore all black, with a skirt round her ankles. She was terribly skinny. She had long hair and glasses and sat in a cubicle, did her work and left at the end of the day. She was called Angie Voigt then."
Pop Tart serves a welcome function in portraying the underdocumented machinery that services fame: the factions who combine to plant a young star on the red carpet with a million-dollar smile. Its central character, is not malign, more a passenger, her innocence exploited by her manager, the villain of the piece.
"There's a message in the book," insists Kaye. "Hollywood is not all glitz. Celebrities are human and go through stuff. Anybody I work with has problems." Ms Spears would no doubt agree.
Pop Tart (£6.99) is published in paperback by Avon, an imprint of HarperCollins