This actually makes me angrier than any part of your story besides the rape. Teachers have NO RIGHT to promise to keep a student’s secrets. They are mandatory reporters. Telling a distraught teenager to trust them is irresponsible. If someone has been or may be assaulted or abused, they have to tell. That’s true whether the person confiding is the victim or the perpetrator. She should have informed you of potential outcomes.
Ok I’m done.