I'm Mackenzie Wellesley, and I've spent my life avoiding the spotlight. But that was four million hits ago. . . Blame it on that grade school ballet recital, when I tripped and pulled the curtain down, only to reveal my father kissing my dance instructor. At Smith High, I'm doing a pretty good job of being the awkward freshman people only notice when they need help with homework. Until I send a burly football player flying with my massive backpack,...