In the past few years, Emma Stone the smiling Circe of the green eyes, sultry voice and fetching overbite has been pursued by zombies (Zombieland) and Jonah Hill (Superbad). In her first shot at a lead, she plays a nice, bright high school girl who pretends she had sex with a college guy and, as the rumor spreads, quickly gains a notorious rep. A breezy update of The Scarlet Letter, the film is an O.K. entry in the subgenre of smarty-pants comedies about young love, like Nick and Norah's Infinite Playlist and (500) Days of Summer. To this mild enterprise, Stone lends winning maturity and a gift for making sassy dialogue sound natural. This 22-year-old is an actress-personality a star around whom Hollywood could build some pretty good movies. Katherine Heigl, watch your back.