That is so awful. If I was her I would complain to the person's superior or the school's Ombudsman. That behavior is totally unacceptable. It doesn't matter what is going on in the other person's life, that is not appropriate. Someone who works with students with dissabilities should be used to working with students with mental illness. If your sister wants to, she should report the behavior she observed. It doesn't just have to be the student or her parents who report unacceptable behavior. Her report should be confidential if she goes to the school's ombudsman.