Nancy, when I was in high school I had a friend, who had some pysch issues, mind you, turn on me. He did numerous things that ended with his file at the local police department a lot bigger, but everyone was on board to ensure my safety- the local PD, the school officials, school security and a teacher of a class that we shared together.
You absolutely talk to whoever you need to ensure her safety at school. Regardless of her age and whatever "toughness" she may portray, going through something like this really rocks one's boat and she's gotta be scared.
Good luck to you guys. ((HUGS))