I'm so, so sorry.
I agree, this kid needs to be shadowed at a *minimum* to protect other female students. Why is the school investigating and not the police? They are going to regret that decision if it becomes public. There was a "hazing" incident (JV football players were sexually assaulted by older players) at a metro area high school. It came out that the cops weren't informed and it's been a huge deal. Schools ar not investigators.
I feel like your DD needs a victim's advocate. I would have no idea how best to help someone in this situation. Again, I'm so, so sorry.