GCSE stress and school avoidance in recently diagnosed daughter

My daughter is sitting GCSEs this year and increasingly stressed about exams. Mocks are next week and it's making her physically ill, she's cried every day in half term about them. She's saying she won't do them, she won't go into school, she wants to drop out etc. She won't take any measures to help her anxiety (breathing exercises, meditation, etc) as, in her words, she's not anxious, just angry that she's being forced to take them. Any mention of exams or revision makes her upset and shut down, so trying to prepare with revision timetables etc doesn't work. We've talked about the results not being important, she's probably knows more than she thinks and might surprise herself, tried to play out the worst that could happen... nothing helps.  Meetings with school aren't helping (although they're doing all they can to support) and CBT isn't helping either. I'm at a loss of what to do when she can't see a way forward, and hearing her say she just wants to die is killing me. She is under medical advice as well but they cant help either. Any advice appreciated