Help me remember the name of this movie please?

All I remember is that there was this psycho fourteen year old who was in love with an older man, but the man wouldn't be with her because of how old she was.She becomes jealous of this woman and later ends up trying to make it look like the man was hurting her at a wedding which leads to him being confronted for a bit by the police and them asking him some questions.Near, the end of the film she has a girl who is a friend of hers I think tied up to a merry go round in an upstairs attic.The man knocks her unconscious and frees the girl the movie ends with her possibly in some kind of place for teenagers and staring at the camera.