Vanessa Walters feels all right. She's studying law but specialising in clothes shopping. She's 19. Her novel's out, and it's going to be big. But the tough part seems to be getting the hairstyle sorted. Amanda Mitchison reports. Photographs by Chris Steele-Perkins
Walthamstow McDonalds on a wet, greasy Sunday afternoon in January. Tired individuals in grubby anoraks, sticky-faced children, chips and cigarette ends strewn across the floor and here, at the table, four teenage black girls, Vanessa Walters, Debbie Constant, Rochelle Dalrynble-George and Bella Ikuemesi, all of them sharply turned out and dripping in gold.

The girls are late for our appointment.

"Oh, we're always late," chirrups Rochelle. "You plan a schedule and then your hair doesn't coordinate."

"It takes me at least an hour for my hair and that's only if I've planned a style," says Vanessa, laughing.

The girls insist that even the simplest hairstyle can be tricky. A ponytail can just stick right out because the hairband is too tight. Or you start curling the ends up and by the time you get round to the other side, the little beasts that you did at the beginning have uncurled. Or the stuff sags and springs back out at you like newly laid wallpaper. Relaxed hair, it turns out, is a misnomer.

Then there is the shopping. On Friday, Debbie was paid pounds 500 from her part-time job and two days later nearly all of it has gone: trainers, a Versace skirt... She is wearing a Calvin Klein sweatshirt ("that's nothing") and a designer shirt underneath. The shoes? "Nothing. Only pounds 70." Throughout the conversation, Debbie fields calls on her mobile phone. Rochelle, who is all of 15, used to have a mobile, but was forced to give it up when her summer job ended and the bills soared. Now she organises her social life through a pager.

Vanessa, a slim young woman in a silver puff jacket, her hair collected up in a mass of curls round the nape of the neck, also confesses to shopaholism. "Since November I've been OK. But I always have in my mind my next outfit. The DKNY section in Selfridges is my real weakness."

We are meeting to discuss Vanessa's book, Rude Girls, an account of six months in the lives of three 18-year-old black girls living in east London. Vanessa wrote the book two years ago, when she was only 17, with the idea of describing the lives of girls like herself and her friends - a readership that she feels modern novels rarely cater for. The novel represents an impressive performance by a writer her age, and, with its youth and ethnic minority credentials, should prove deeply marketable. The BBC has already bought the film rights.

One of the most noticeable features of Rude Girls is the protagonists' inability to arrive anywhere on time. Every social occasion is preceded by hours of mutual grooming: the construction of complicated coiffures with scrunchies, gold shiny bobbles, gold butterflies, combs, grips, elaborate knots, bunches, French pleats, sewn-on fringes and hairpieces, threaded- in diamond stones, and the squirting of colour and sheen spray and setting lotion. All this is followed, or perhaps preceded, by the application of make-up, some toenail filing, maybe a long, hot soak in a foam bath. Then the interminable dithering over what to wear. The legging suit? Or the black sequined bra top? Or the catsuit with the diamond dollar sign? Should Janice coordinate with Shree and Paula? Should Paula coordinate with her three-year-old son, Fabian?

"White girls - they would eat first, buy later. We're the other way round," explains Rochelle. "I feel naked without gold."

Murmurs of assent all round.

"If you don't have a pair of Moschinos you are nobody," she continues.

"Or if you are wearing last month's trainers," adds Vanessa.

But boys are worse.

"One boy I know spent pounds 900 on a jacket," says Debbie.

"There is this friend of mine, he'll remain nameless," Vanessa recounts, "I phoned him up and I said 'How are you?' He replied, 'I got my Stone Island jacket.' Not 'I'm fine' or anything. Just his Stone Island jacket. That was him - he was his jacket."

Rude Girls features a shoot-out, a car chase, drugs, high-rise estates, underworld figures who turn up for fights at parties. One of the protagonists is a single mother, another lives off the earnings of her drug-dealing father and falls pregnant by her boyfriend. Only one, Janice, comes from a "respectable" family and wants to hold down a job. It's clearly a harsher, more violent world than that of Vanessa and her friends. "I suppose it's a bit exaggerated in places," confesses Debbie.

Vanessa wrote the novel when she was at Queen's College, a very unrude girls' private school in Harley Street, London, where both she and Debbie were pupils on the assisted places scheme. She used the school computer to print out scrolls of text which were then read by Debbie, who proffered suggestions, and who still has the old drafts in her attic. You can imagine them sitting in the homework periods - two of the very few black girls of their year - quietly discussing whether the attack in the car park feels right, or what sort of bracelets a drug dealer would wear.

"A Rude Girl," explains Vanessa "can mean a really bad girl - or it can just mean someone who is feisty, sassy, does her own thing. Is a bit streetwise." And Vanessa and her friends, although they may dress to kill and go to all-night raves, are only rude girls to a very limited extent. For on closer questioning the frivolity turns out to be pretty skin deep. The girls don't drink - well, not much and not, as Rochelle points out, "like white girls who say, 'let's go out and get slaughtered.'" They disapprove of promiscuity - nobody wants a reputation as a "slusher" - and they wouldn't consider having a child until they had settled down, or married.

The girls are all in full-time education, and all intend to follow careers. Vanessa and Debbie are now at London University: Debbie is doing computing and business studies with the intention of becoming a systems analyst, and Vanessa is reading law and hopes to become a barrister. It seems a sensible, career-oriented choice of subject, but for Vanessa law was the softest degree option she could get away with. She says, "My father wanted me to do science. Law was better than nothing."

Parental expectation has clearly had a strong influence. Three of the girls come from broken families, and all have mothers who work. (Vanessa's mother is an administrator for Walthamstow council.) As Debbie explains, "When you see your mother working hard, then sitting at home watching telly - that's not on." Vanessa did move into a hall of residence for her first term at university, but has now returned home, largely because of pressure from her mother, who suspected her of not working. Mrs Walters has already decided that she wants Vanessa's sister - who is five years old - to become a doctor.

Vanessa, Bella, Rochelle and Debbie all live at home under the maternal beady eye. Vanessa mentions her mother turning on the loudspeaker button upstairs when she is on the telephone and opening her post accidentally-on-purpose. Debbie's mother, meanwhile, insists that there is "no such thing as privacy in my house". When Rochelle brings a boy home, "My mum does, 'I don't like the look of him. He looks shifty. Did you see his trainers? How can you let him in with dirty shoes?' And she says when he's out the room, but so that he can hear, 'get that ugly boy out of my house.'"

"I gave each of the [female] characters a quality I admired," explains Vanessa. "Paula is tough, I really respect her for that, people can't mess with her. Shree is nice and sweet and kind to people. And Janice, she wants something better for herself."

Which brings us to the men in the novel. Why are they all utterly worthless? Michael is a devious philanderer, Nero a dangerous criminal, Maurice an insufferable prig, Elroy a bully, Tyrone a drone or, as he puts it, "not a bills type of person". Admittedly the last two are both OK by the end, when they have been pulled into shape...

Here Bella, who has been silent throughout most of the conversation, shrugs her shoulders and says in the tone of someone stating the very obvious, "But all men need pushing into shape."

A young black man, with the word "Valentino" embroidered across his anorak, walks through the door. The girls' eyes swivel round to follow him as he makes his way to the counter. There follows a small stir of admiration, raising of eyebrows, flicker of interested expressions...

"Now," proclaims Rochelle, "there's a jacket for you."

'Rude Girls' by Vanessa Walters is published by Pan on Friday, price pounds 4.99