When she's itty bitty and blond, wearing ribbons and curls and an aura of money, she's adorable and vulnerable, the tiny, innocent heart of our culture. But when the little girl comes from the working class, she's something else. Just what, and why so little is said about it, are the questions Valerie Walkerdine asks in "Daddy's Girl, " a book about how we see young girls, how they see themselves, and how popular culture mediates the view.