Single-White Female by Bridget Fonda

Single-White Female stars Bridget Fonda as Ali, a 20-something fashionista-computer programmer who lives in the historic Manhattan apartment building. At the beginning of the film, Ali is shacked up with her boyfriend Sam played by Steven Weber. But one night in bed they let the machine pick up the phone and Ali hears Sam's ex-wife leaving a message revealing their sexual relationship isn't really over. She kicks Sam out and puts an ad in the paper, looking for a roommate.