What they should have done, if anything, is talk to the girl about the rules against threats of any kind. A felony charge for this? The adults who did this should be fired.
My middle daughter received a 3 day suspension for making a threat to another girl who was being a bitch. She told her that “life was like a wheel and one of these days you’ll get whats coming to you.”
That was the last day she graced their halls as a student. And we live way out in the dirt part of Kansas.