It sounds like it would be difficult at this stage of her life, but do you think you could get her to sign a durable power of attorney? That’s the best way to take charge of her health care needs.
If there are other siblings/family members they could challenge mental ability of Mom to sign such an order. Should have been done long ago, Lesson for all of us.
POA does nothing in terms of medical care. You would need to get a guardian appointment. That has to come through the courts. Then you have to “section” her. I had to do that with an aunt.
Once she is in a clinical setting you will have more say with a Healthcare Proxy.
Without that legal paperwork, you are SOL.