Hi,
I am sorry to hear all you have been through. I took care of my in-laws and after my mother in law passed we had to move my father in law in with us. He had a few health issues but nothing major. He did not want to do anything but sit and watch tv and sleep. It got to the point that he could hardly walk and was falling a good bit.
His primary care provider told me that it would only get worse over time. He knew that I also lived with chronic pain. His advice to me was to put my father in law in to a rehab for a while so that they could work with him. He really did not like the rehab because they made him do PT and move.
After he got discharged he would do his at home PT and move more because he did not want to go back to rehab. Maybe that is something that could help you with your Mom. I wish you the best
Gentle hugs
TPC YaYa