School as in college? If so, you aren't obligated to finance her higher education; especially, if she is treating you so badly. Also, you aren't obligated to discuss these issues with your mother. If you insist on answering when she calls, then be ready to say...sorry, got to go, if she starts in with the daughter issues. She'll figure it out after a while.
It may sound cruel to you to do these things, but you're the only one who can make the changes necessary so you aren't going through this stuff.