She walks down the street on the Upper East Side, thin and stylish, another well-heeled beauty chatting away on her cellphone. Except that she isn't — she's Osama bin Laden's niece. Wafah Binladin left the city in the months before her uncle's ghastly attack, but she's back now, living at a friend's posh pad off Park Avenue, pursuing her career as a pop star and living it up on the social scene at swanky Soho House. A former Columbia student who grew up in Geneva, she takes the subway around town, Elton John sheet music under her arm, trading on...