Does anyone know the name of this movie?

[markymarkk]

I saw this movie years ago with my mother. I don't remember the title, and neither does she, but I do remember some of the details of the movie.

The movie was about a girl who was a single child and lived with her mother. She became friends with some other kids around her age. Things eventually got ugly. I remember there was a scene where they had a fight in a parking lot and she got beat up.

And then not long after that they showed up at her house when she was home alone and tied her up and slit her throat in her bathroom. (I believe she was wearing white?). Her mother came home and found her like that.

I've been trying to find someone who knows what this movie is for years, hopefully someone here can help me.