Lipstick (1960)

Tween girl Silvana develops a crush on her handsome older neighbor Gino, whose flat is across the street from hers. After a prostitute is found murdered in her building, she tells him she saw him visiting the victim a few days before the murder To keep her from telling the carabinieri what she saw, he takes her to a movie--which encourages her. Then she sees Gino with his fiancee, and their flirtation intensifies. Is Silvana in love with a killer?