How to convince a very belligerent, changeable and mobility challenged 91 year old that her house is no longer the right place for her?

Our mother is 91; she still lives in her 5 bedroom suburban house, though her life has become restricted to three rooms on the first floor. She has had arthritis and spinal stenosis for decades, and her mobility continues to deteriorate. She now walks from room to room with a walker. Getting her out of the house is difficult and requires a wheelchair. Mother often has trouble getting out of bed or out of a chair. She has incontinence and is prone to UTIs. She occasionally hallucinates, and she does experience sun-downing.

But she is lucid enough to make everyone miserable with her mind games. For a couple years, my Elder Sister, Brother and I took turns staying with her or visiting her, but that was wearing us out - especially Elder Sister, who is now 63 and semi-retired. (I am 60 and about to begin semi-retirement. Elder Sister lives about 40 minutes away from Mother; I live 200 miles away.) Over the past year, we have been bringing in home care workers, all whom are independently hired and paid by us. After Mother suffered an incident of extreme confusion and incontinence two months ago, we went to 24 hour care. Mother hates having people in the house, but gets very upset when she is alone. She is sometimes nasty to Caregivers, and insists her family should be coming more often.

Half of her house is owned by a trust created by her late second husband (Not our father; our father died 40 years ago). We have sought legal advice and been told we'd be best off selling the house and liquidating the trust. The remaining step-sisters agree. So we began working towards that, with the deadline of selling the house and moving mom set as this summer. We found an Assisted Living facility nearby that permits her cat.

Well, although we have talked about this repeatedly, Mother is refusing to move. We have taken her for lunch at this facility, which we all agree is very nice. She says it's a dump, and she'll keep her house and when the money's gone, she'll go into a welfare facility. When confronted with the irrationality of that, she gets violent and verbally abusive and isolates herself.

The person who is most profoundly effected is Elder Sister. She visits mom up to four times a week, schedules the help, pays them, shops. . . . . She has also been doing all the legwork on finding a facility, and seeking out legal advice. Elder sister is so stressed and overworked, she doesn't even have time to write a note like this. I fear for Elder Sister's health now. I live 200 miles away. I go to Mom's once a month for five to seven days; during that time I am primary care giver. Our other three siblings, two of whom live within ten minutes of Mom, are fairly unreliable. (The Brother mentioned above is a pilot and often out of town, if not out of the country.)

I know there are a lot of issues here, but Elder Sister and I are beside ourselves. Any advice on any aspect of this wasp's nest, or stories about negotiating similar situations would be welcome. Thank you!