How do I help my mother keep her money for her own care?

My parents lived with my family for over three years. Then, my mom's dad died and left her enough money to buy herself a home, cash outright. It was only five minutes away from my house, which was nice. Unfortunately, within two years my dad died of cancer. We went to Mom's house literally every other day to help her take care of everything from setting alarm clocks to lawncare and doctor visits. My children are very close to her and she to them, but we rarely get to see her anymore. About three years ago my sister and her husband showed up at Mom's (unannounced from out of state) and said they had to move in with her until their tax refund check came in about five months later. Needless to say they never left. My sister has never worked, her husband finally works, and they have three kids in their twenties and various pets living there as well. One of the the kids works about ten hours a week and the others do not work at all. They are all over 300 lbs. apiece. Mom's furniture is all broken because they are too heavy for it and they have taken over her house by sleeping all day and staying up all night on the internet. They have put on about 100 lbs since moving there. The rest of the family can't visit Mom there anymore because they're always sleeping all over the living room floor etc. Mom EASILY had enough money to last her the next thirty years and still be able to leave her four children an inheritance. Now the people at the bank who run her trust fund (and have her living on an allowance) have told her that they are running through all her money and that she if she does not ask them to leave, she will be looking for a place to live herself in the next six months. I know her bills are all astronomical, most have tripled or quadrupled from what they were. Yet my sister and her family don't seem to care and actually got angry at the bankers for telling them this. The lawyer at the bank contacted me hoping I would be able to have some influence but I fear I have none anymore, she just gets made when anyone says that they need to get jobs and move out instead of mooching off her. I still have her power of attorney over healthcare. My other oldest sister is the executor of her will. We are both appalled at the situation but don't know what else to do about it. Now my sister is trying to get her to cancel the trust fund and sell her remaining stocks, put everything in a checking account, and do a reverse mortgage on her house so that my mother can continue to pay for them. We don't know what to do short of having Mom brought in for a sanity hearing, and certainly if we did that she'd never speak to any of us again; although it might be worth it if it would let the bank keep her trust in place so that she has enough money to live on the rest of her life, she does have many medical issues and will most likely need some type of assisted care in the near future. For someone who claims to be a Buddhist and a vegetarian, my sister spends an awful lot of Mom's money on meat, beer, and cigarettes. Right now she does cook for Mom, although it's always something she shouldn't eat given her medical conditions; and Mom says she cleans but you can't actually see most of the house because of all the extra people and extra pets and extra stuff.) No one really would mind if just my sister and her husband stayed (if they actually took care of Mom instead of just leaving her to lay in bed all day) but those kids definitely need to go before she becomes bankrupt and homeless. I have talked to my Pastor about this but he did not have any ideas either, and there are dozens of people at our church concerned and praying for her in this situation. It's like a bad soap opera. Any advice you can give before Mom is homeless and penniless and the rest of us lose what's left of our inheritance would be most appreciated. THANK YOU!