As the fashion-forward half of the Olsen Empire, this girl was counting her millions before she was old enough to drive. Not surprisingly, it's Mary-Kate's quirky style that has earned her full membership of America's best-dressed under-25 clan, alongside Lindsay, Nicole and Mischa. She only has to nip out for a skinny latte in retro Ray-Bans and a baggy jumper to set tongues wagging. "MK knows exactly how she wants to look," says her hairdresser Mark Townsend. "It's no surprise that girls across the world try to copy her." Not that she makes it easy for them. "She's gone from honey blonde to white blonde to brunette to strawberry blonde and back to honey blonde again," he says. And she's flirted with a range of styles – from glam to boho. And she's only 21!

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