Whats this movie called?

the movie is about: a girl who sees evil inside people and she saved a girl from the evil inside her but the mom wacked the girl in the head and killed her. there was a black girl with a neclacwe the evil girl wanted to she took it after she tied her up in the good girl's dad's shed. The evil girl but a razor in a good's girl friend's choclate bar and cut her tongue. Please someone answer correctly i wanna se it again.