Ive got a very simple souloution for you. I dont endorse violence.... but i do endorse pranks...

If she takes her cell phone to school, try to get ahold of it and set an alarm on it for sometime during class. taker her toothbrush and scrub floor grout with it. better yet, scrub the schools floor grout with it. fill her drawers with itching powder. or... well, i might have something. i have a chemical that dissolves a small layer of skin. not enough to hurt, but enough to bleed. put it on toilet paper before she gos to the bathroom.... trust me, it really relieves stress and anger to get revenge like that.