Mom is saying others are mean to her. She even said that my sister and husband hit her. Any advice?

And the other sister threaten to hit her.
Mom is in the Alzheimer's unit and has Parkinson/dementia-I was there at the nursing home on Sunday when my sister & her husband came. I even rode over with my other sister to see Mom and no one did anything to Mom. My sister lives about an hour away and works(she's a nurse) so she only comes over about every 6 weeks or so. What is making Mom have these feelings? She had told me on another day that this man had a pocket full of money & she was going to marry him.
The reason Mom ended up in the Alzheimer's unit is because she wants to get up all the time and has fell 6 times in 5 months and the last time was the worse. Parkinson makes her fall backwards instead of frontward and she still has a small knot on her head. The emergency room doctor had an MRI of her head done and she does not have a concussion(abt 7 wks ago) Thanks