Is it legal to cut off my sister from visiting my Mother?

It is considered Elder Abuse to isolate her from family. If it wasn't, I'd ban my brother. If they call Adult Protective Services, you could get in a lot of trouble legally. Truthfully (and I definitely understand), you are doing this because YOU are angry at HER. That's not fair to your Mom. Believe me, I know how you feel 110%. You can, however, put limits on the visits (like they can't take her off the premises), I believe. Sorry. I have a nasty brother who is very manipulative. But my Mom has fallen several times when I've been in the house.

If your family is engaged in a legal battle over who takes care of mom or who gets to see mom any contact should be done through your lawyer.

My mother fell while in short term rehab. Luckily she was alright, but I didn't blame the facility. Falling is quite common in the elderly.

BTW, sometimes old people fall. If your sister was neglecting her or pushing her, I could see some blame being placed. But if it was just falling, no blame could be placed. It just happens.

I don't see any reasons to restrict visits unless your sister is harming your mother in some way. Not showing up to me is not a reason to tell her not to come visit. I feel I am not understanding something here.