My mom has dementia and is in a nursing home. Since being there she has declined?

She was going through therapy, but they stop, because she refuse to cooperate. She had fallen a few months ago and her doctor informed us she couldn't stay by herself. She was getting around, using a walker, going to the bathroom doing her daily activities at her own speed. Since she has been in the nursing home, she has declined a lot. They stopped her therapy and explain that they could force her go do therapy. I am not understanding why. I thought that when you were in therapy they (I don't want to say force), but at least push her into trying. She weighs over 200lbs and has pretty much given up on trying to help herself at all. Refuses to walk (she can with a walker), wets herself constantly, doesn't want to raise her arms at all, says it hurts to much, have gone through test, but they cannot find anything wrong. We try and spend as much time with her and one of her activities was going to church on Sundays and Wednesdays, but know it very difficult to do this, because she offers no help when trying to get her in the car. She fights us, but yet gets upset, because she is unable to get into the car. My sisters and I are just trying to understand this. Anyone else had to deal with this issue.