Hi there. I'm so very sorry for the challenges you are facing. I have some thoughts that might be helpful.

1. Do not blame yourself. I know it's hard to - as a mother we feel responsible for everything - but your child's neurobiology is different and she either has a mental illness and/or different neurology. She is severely disabled, by no fault of your own, and accepting this will go a long way in helping your own sanity. It's like living with an addict: you didn't cause it, you can't control it, and you certainly can't cure it. So give up on those things and focus on your health and safety and the health and safety of the rest of your family (she might need medication? sounds like you have a team, has she had a formal neuropsych eval? if she had a diagnosis that could help a lot)

2. There are many techniques that help with grounding and calming. Contact points, 5-4-3-2-1 technique, taking time outs, taking deep breaths... I encourage you to research it and try putting them into play

3. Many people have said get support/therapy yourself and try to get some respite and I think those are crucial, if at all possible.

Hope this is helpful.