Etoile has it exactly right. Keep a record of what this nut case is doing and make sure that womeond "in authority" also knows what is going on. You should not have to go through this alone and I am very disappointed in your school's answer-make sure that you document that also. Block her IM's and stay away from her.....
"I'm mad, you're mad. we're all mad"...
The Cheshire Cat