When you first left me, I was wanting more/But you were fucking that girl next door. With these gentle words, Lily Allen entered the breakup-song hall of fame, singing “Smile” to her ex with a breezy sha-la-la lilt that just made the song seem even nastier. The girl’s got a mouth on her. She blew up in the U.K. last year and already has a sizable cult here, so the U.S. release of her debut album, Alright, Still, is belated yet welcome. In the tradition of Annie, Robyn and Stacey Q, Allen is a theoretical pop princess whose U.S. audience consists mainly of lonely-guy literary types. The twenty-one-year-old London brat writes shambling pop songs, rooted in ska and rap, with cheeky rhymes — she never sounds like she’s trying too hard. In “LDN,” she walks through the city checking out pimps and crack whores, because “the filth took away my license.” (That means the cops.) She gushes about how bright and sunny London is, and you sure don’t hear that every day — but it’s just more proof that Lily Allen’s an original.