Which film is this?I saw some part of it while watchin TV & wasn't able to find out the title?

I don't know the name of the heroine but she plays a character who works against child abuse & saves a girl who was going to be killed by her parents & then she asks the police if she can live with her.The police agrees but soon she finds out the girl is an avatar of the devil & has actually killed all her aunts & uncles.The girl also kills her boyfriend who was a phsycologist.I didn't watch the whole film.