Tough times

My sister recently came to Oklahoma to get my mom and take her back to Atlanta. My moms been gone 3 months and is now coming back home. The problem with that is, my Mom is having very serious health problems. We've gone to doctors for 2 years and no one can tell us why she's falling everyday. Falling sideways, not just tripping but completely losing all muscle tone and dropping. She's losing her memory and words and just not with it somedays. I think she has the beginnings of dementia and I believe it started with severe depression from my Dad being killed in a car accident 6 years ago this month. She's never been the same since.
All I want is for her to be safe and healthy. I can't seem to make that happen and it's killing me. I'm so stressed I don't even want to leave the house or do much of anything.
I'm researching assisted living facilities and hoping to find a good one in the next town. By the way, buy long term care insurance now because assisted living is close to $5,000 a month. Amazingly expensive.
I was hoping my sister would help with my Mom until we could find a place in Atlanta near great doctors but my sister is completely selfish and is sending my Mom home because she needs time with just her (grown) kids and husband she doesn't even like. I really doubt I ever have a close relationship with my sister after this. Somehow the child (me) with growing children and a full plate always seems to be the only one that can take care of our Mom. My sister is retired with a 25 and 23 year old yet can't take care of our Mom for 6 months while we figure something out. She said I owe he'd money for taking care of our Mother. Greedy and self-centered.
I'm hoping my Mom gets home and we can find her s great place to live. I'm praying something works out for us. It just has to or I might drown in my tears.