Bad Karma (2001)

A young girl is abducted by a man who claims that she was the one who killed him in a past life; when she denies this, he forces electroshock treatment on her. Eventually her personality changes and she kills him and walks off. Years later she runs into a man and says that they were lovers in a past life. He of course thinks she's out of her mind, but she pursues him and tells them that they were more than lovers: they killed people together.