Can't Remember this Horror Movie?

I can't remember the name of the movie, but it was a horror movie. The scene that I remember was that a snobby bully girl was tied up and was going to die. It was also the same day of her birthday. The girl that she had bullied had the opportunity to save, the bully girl then kissed up to the girl she bullied as she began to free her former enemy. As the bully is almost saved she accidently says something condescending to the girl she bullied, and the girl she bullied just leaves the snob to die. What movie am I thinking of? I think the girl that was bullied was one of the main characters in the movie.