Can we officially stop worrying about girls now? From the sad and starving girls of Reviving Ophelia (Ballantine, $7.99) to the really mean girls of Queen Bees and Wannabes (Crown Publishers, $24), an entire industry is devoted to chick-related handwringing. The culture damages their fragile emotional lives, people say. Girls are afraid to speak up for themselves. Math teachers don't call on them. They bully each other to cope with their systemic oppression. Yet, somehow, teen girls seem to be doing just fine. They are proud of their bodies, showing off all manner of bellies below their baby-sized T-shirts. They...