I suggest you contact an attorney in your area and go over all the legal options available to you.
Certainly an harassment/stalking order could be issued preventing her from further acts against you, a defamation action is possible for the libelous comments made about you on MySpace (if you can demonstrate reputational injury has resulted from these comments and you feel spending the time and money that such an action would require would be worthwhile), and an identity theft/fraud suit could potentially be filed against her, for ordering items in your name.
If I were you, I would file a police report, detailing the harassment and identity theft. Then I would contact an attorney to see which of the above options makes the most sense in your situation, based on all of the facts you present. A cease-and-desist letter drafted by an attorney and sent to the teacher, detailing the various legal actions that can be pursued, may be effective, as well.
Good luck.