Per the above, they know who did it.
But are refusing to say.
Doesn’t this girl have any recourse in the matter? Her reputation was attacked. Her life was put in danger to the point she was escorted to classes.
It was probably either a male who she turned down for sex or a female that she had sex with her boyfriend. In either case, before long, the Police will find her dead body in the woods or by the roadside in a ditch.