It's great that you are having therapy, because you need your own space to vent and talk things through.
Has she had any other assessments besides her mental health issues?
Have there been any traumatic/triggering events in her life besides anxiety? Including bullying, previous schools not dealing with her needs etc.
It all sounds exhausting,terrifying and utterly heartbreaking so I don't blame you for feeling like you do.
As hard as it is, try and focus on what she does do. She gets up every day,she gets ready, she attends school, she engages at a certain level. She's still trying and she's still going. She hasn't given up.
Try and engage with her interests (if she'll let you) even if it's all scrolling on the phone. What apps are they,what is she watching, can you watch together?
Ask her to join you for a movie or a drive . Easy and chill stuff with no expectation. Just to remind her you are there , you're not going anywhere and that whatever she's doing is good enough.
There seems to be a lot of focus on what she won't do,what she can't do, what she's expected to do and she doesn't. Expectations. I don't know if this is apparent in real life or just on here, but if it is , it won't help her ,at least at the moment.
What worries me the most is the possibility that something was missed in the underfunded ,overworked chaos that CAMHS is. It's obvious your daughter is very ill, but do they have the right cause/diagnosis for her and treatment/course of action for her?
Can you afford to go private?