Putting this out there in hope of some additional advice. I have had POA for my mother for about six years, live 165 miles away and have made numerous trips for various health crises. My brother has been part of this first responder process, but lives 650 miles away. A third sibling is disabled, lives 300 miles away, and has pressured my mother to sign a statement, and/or change the existing will to state that the family home should be sold to her and her husband. They have also tried to get my mother to agree that they should move in and take care of her. Besides being disabled, our third sibling has voiced intentions to take her own life due to her serious physical problems and has a history of being highly litigious. It's not reasonable to believe that this would be anywhere near a reasonable solution for our mother. When we are not physically present, there would likely be an attempt to have my mother alter the existing will. Recently we had to have family members present during a visit to the house. Our sibling was accompanied by a bank official (posing as a personal assistant) who we suspect was prepared to notarize any document, and possibly carrying video/audio devices. We have received some advice, but wondering if anyone has additional observations that could help us deal with this.
Is there any chance that Mom will run out of money for this 24/7 in-home care she is receiving. If there is any possibility of needing Medicaid somewhere down the road, then you also have to be very aware of anything that looks like your mother "gifting away" any of her resources.
How much in agreement with your assessments is your mother? I think that is key.
I don't know of any way of preventing your mother from making her own decisions, changing her will, etc. Is she likely to take advice from you and your brother? Convincing her not to have disabled sister in as a caregiving, etc. may be the best you can do.
Would you object to your sister buying the house at a fair market price after your mother dies?