What are some daily activities for someone who has Parkinsons-dementia?

My fiance and I moved in to help care for his grandmother, whose disease has progressed into late stages and her life partner could not continue to do all the work. Combined they have 25 cats in the house who some also get minor amounts of care (beyond clean litter boxes and fresh food and water). It's a clean environment and it's what they have done for many years. However they prioritized the cats health to their own.

Not long ago her life partner went to the hospital with chest pains and ended up in need of quad-bypass surgery. She decided to recover elsewhere for the sake of not having a cat end up jumping on her chest. My fiance immediately had to take a leave of absence from his job, while I had already quit my previous caregiving job to move in. We began taking care of her and all the cats around the clock. She is still mobile and can care for herself hygienically with some encouragement from us. We have to give her pills every three hours, and make her a meal and convince her to eat within an hour and half time frame between pills. We have taken on all of the responsibilities that go into caring for her as a whole. Her son and his wife have come to help but it's very difficult for them working full time and attempting to play catch up with where to go with her care from here. Her life partner after recovering from surgery decided to not come back at all unless she is sent to a group home. We are caught in the middle of this "divorce" and feel our kindness has been taken advantage of. This is indefinite and I believe my fiance will have to quit his job.

Our problem is that his grandmother, loves to be working and problem solving. She likes to be left alone much of the time to do her random housework activities. But she can't start and finish a single thing that she does. She takes cats food and water without ever giving it back, mixes them up in their kennels, moves everything around the kitchen, hides things I need and is constantly going through papers or anything she can find. I once found her outside screaming at night with a flash light because she thought there was a missing cat. If she doesn't have a problem she creates one. Now we also have to remind her that her partner is not coming back. Two weeks ago she would call out for her partner and we could tell her that she is not here but at a relatives house and she would accept that answer. More recently she does not believe us and continues to have delusional conversations with her partner and deceased mother. She says words clearly but can't construct a sentence. She's emotional and angry frequently, she sundowns and picks fights with us but she can't tell us why she's mad at us. She'll put together whatever she can to tell us we're doing a bad job.

Last night she had a blanket over an office chair and she dressed it with a shirt, having conversations and bringing random things to it. Tonight she has a cat bed and blanket in her bathroom, which she believes contains a newborn opossum, another thing she did frequently when she was younger. I let her think it was there for the benefit of it was comforting and she was not trying to fight with me.

I need to lock the refrigerator, all cupboards and doors before she hurts any cats or herself or breaks/ throws away any of our stuff or important things in the house. I need some sort of entertainment for her, something she thinks is her working and helping. She won't watch tv and she can't write. She likes to work with tools but it can't be anything to sharp or dangerous for her. I am also setting up Alexa so I can begin playing music for her. I want to keep her safe and occupied from the emotional turmoil that we are all going through having been abandoned.

We both just turned 21 and are struggling with the reality of how drastically our lives changed so quickly, while trying to bare the responsibility and put our own emotions aside. Any advice deeply appreciated.