She is a Time magazine covergirl and already has been on the cover of pretty much everything else and last week she was named as Tatler's most stylish woman of the year.

She is the face of this, the body of that and the spirit of the other. Already, the rails of Topshop are flogging copies of what for months has been fetishised on the fashion pages as her signature style. Already Zara has ordered mannequins based on her. No glamorous event is complete without her. She is the hottest new model on the planet and she is adorable, unstoppable and every inch her own fresh, maverick woman. She has achieved all this, in shocking defiance of the rules of female beauty, with Short Hair. It is a fashion miracle.

For those innocents among us who are not A-star students of fashion-media hype, Agyness Deyn is not quite yet a silly name they have learnt through osmosis to pronounce and spell. Actually, the former is no problem, as you just ignore the tortured spelling and say, "Agnes Dean". The latter, if you are interested in spurious etymology as well as tortured spelling, can even be gilded with a footnote.

It explains that young Laura Hollins chose Agnes Dean as her going-to-be-famous name, while her mother, Lorraine, somehow conjured the look of the name - its styling, if you will - by applying some of the wisdom she has gained through being a master of reiki healing. Or after reading an article about numerology in a magazine. Depending on what you prefer to believe. Anyway, it is not whimsical, this name, it is serious and somehow spiritual. And edgy. Or something.

Sadly, the whys and wherefores of this process of name transformation are currently inaccessible, as Lorraine has told the media: "I'm very proud of her but I have been advised by someone acting on her behalf not to speak about her and I'm not even prepared to say who." This is just as well, for already the truth has proved irksome to the fragile myth of Agyness Deyn.

The business of fashion myth is greedy and even though Deyn is only 24 now, it is alleged that her model card claims she is 21, and that in an interview she said she was 18, provoking a gaggle of schoolfriends to point out that she used to be the same age as them. Maybe it was thought that the younger Deyn could be, the better, as far as filling those Topshop rails was concerned. It seems a bit of a shame when 24 is considered not a desirably young enough age for international stardom but nobody ever said that fashion wasn't youth-oriented.

The hype world, also, prefers the idea that she was talent-spotted while working in a chip shop in Stubbins, Lancashire, to the rather more believable alternative, which is that she was spotted by a subject-hungry photographer in the rather less unlikely venue of a hip vintage store in London's Kentish Town, dressed in all the finery that a style-conscious young beauty on the lookout for opportunity could be expected to muster.

Deyn did work in a chip shop but while she was at school studying drama and music and already modelling locally with some success. She was already interested in fashion, already the winner of a local modelling prize and already planning to storm the London scene with her friend, the fashion designer Henry Holland.

Holland is described as a childhood friend but again the truth is slightly less primal: he ran into her when she was in her mid-teens at the venerated chip shop and they recognised a kindred spirit when they saw one.

Now the two of them are projected as wide-eyed little ragamuffins, stumbling innocently towards London in the manner of Dick Whittington and his cat, and brave enough to say goodbye to the chip shop and face outrageous fortune because they had each other. Again, it's a nice romantic story but the truth, as we know, is that the Manchester area is extremely far from being a youth-cultural desert. Somehow, in the rush to mythologise Deyn, it is more convenient to pretend that it is.

It is strange, this desire to believe that Agyness Deyn is the young and naive creation of the fickle finger of fate, because what has been clear from the first stirrings of fashion-media interest is that she is a confident young woman with a highly developed sense of her own likes and dislikes. Deyn's style, anyway, is "idiosyncratic" in a way that has been familiar to followers of street fashion since the '70s. Jaunty trilbys, stripy socks, braces and rock-gig T-shirts are hardly items of clothing invented by her.

Deyn's idiosyncrasy lies only in the way she continues to dress like a style-conscious girl on a budget, instead of going belly-up before the blandishments of the designers who would very much like to dress her for absolutely nothing. (Not that she turns her nose up at a nice dress for the red carpet.) Her look is, in that respect, shrewd because it marks her out as "normal" in a business that is more comfortable with abnormal. That's what got her spotted and that's what got her work and attention.

Are these minor confabulations important, even though they are far from new? I'm inclined to think that they are. There's something rather pathetic about the widespread desire to believe that Deyn is the passive recipient of her success, rather than the active architect of her career. The idea that nice girls don't want to have huge careers but instead have them thrust upon them really ought to have been consigned to history by now.

Deyn is reported by all who know her to be down-to-earth and straightforward, fun and decent. There's something of an implication, in the attitudes shown towards her back story, that an acknowledged desire for success would run counter to these attributes, in just the same way as going to private school or having an uncle in the business is considered to be the sine qua non of cheating corruption, however talented you may be.

Certainly, Deyn herself is in no hurry to challenge the way she has been packaged. The little she says in interviews is very much in the traditional vein of self-deprecation. She claims not to varnish her toenails because: "I've got really bad feet - they're so bad they're good." She also likes to go along with the idea that she "is not sexy", as if the divide between glamour models and fashion models never existed before she came along, and as if the triumph of a tall and willowy blonde with perfect skin somehow rewrites the story of 21st-century female pulchritude. Anyway, the vulgar T-shirts of her chum Holland, saying "Flick yer bean for Agyness Deyn", appear to find buyers, even though no one is supposed to find her remotely fanciable.

Deyn is aware that her championship of street style is a part of her image that brings in lavish contracts with luxury firms and is not above whispering such lines from the PR handbook as: "I love Burberry and it's special to work for a British label." She flogs the British angle like mad, posting a photograph of her heroine, the Queen, on her website and flying a little Union flag off the back of her bicycle. All this adoration of England, must, of course, go down a storm in her adopted home of New York, where being as English as fish and chips, and even having served them, is even more of a novelty than it is in England.

There can be no doubt that Deyn is poised to become famous and rich. There can be little doubt, either, that Deyn is happy at the prospect of such an outcome. I'm inclined to think that her keen desire to go along with the idea that all this is just something that was thrust upon her, is itself evidence of just how well she understands how popular culture works and how much the luxury market relies on its association with youthful street styles in order to make its elitist pile. Deyn would never be crass enough to say that she wants to be massively wealthy. But she's laying the foundations of empire.

I'd be surprised if Deyn turned out to be the doomed kind of It girl rather than the savvy kind. Part of her compliance in going along with the media game appears to come from the understanding that, if you play your cards right, you can live in front of the cameras and still keep your private life private, as long as you follow the rules. Deyn turns up at the parties fashion throws but she is never seen staggering out of them. She is always working, except when she is behind closed doors, and she shows every sign of being able to keep it that way. There will be no profile-reviving reality shows for her and no florid brushes with tabloid scandal.

The real story of Agyness Deyn is that she understands just what she wants and just what is required of her if she wants to get it. So far, all her dreams and plans are coming together nicely. There is no reason to imagine that she will ever stop rising without trace or ever regret her very deliberate choices.