My grandmother is almost 90 years old and four years ago when my grandfather passed away we moved her sister in to live with her. While it seemed like a good idea then, we later found out her family was coming and stealing things from my grandmother, making my grandmother wait on her hand and foot, and had so many surgeries that she can barely do anything for herself. None of her children want anything to do with her because she is so mean and the doctors won't waste their time on trying to help us. She needs around-the-clock care she is continuously falling and is threatened to sue if she falls and gets hurt. When we tried to step in and help find a nice place for her to go she made things horrible and made my grandmother feel guilty. My dad is the power of attorney over my grandmother we just want to know what is best and what we can do! Please anything is better than nothing we have tried everything!
2) After the sister is settled, move grandma home with caregivers.
3) Everyone will understand that the sister required more skilled care and was admitted permanently.
But I do have another thought, too. I appreciate that it seems a bit unreasonable for your grandmother, at ninety, to have to become her sister's full-time caregiver. But don't be too quick to assume she can't or won't want to do it. My great aunts lived independently but ended up sharing one home; and I later came to realise that the older, then in her late eighties, had nursed the younger through cancer of the jaw right through to the end of her life. It must have been harrowing; but she took it in her stride, in spite of having had no nursing training or experience. It was something she wanted to do.
So the family needs to talk to both your grandmother and the two sisters together and find out what they want. If it turns out that neither wants to move or wants the other to move, your father should use his POA to insist on plenty of in-home support so that your grandmother isn't run ragged with work she can't manage.
Ref your great-aunt's thieving relatives - you say they come to the house and steal, then you say they don't come because your great-aunt is so mean. Which? If they're still turning up on a regular basis, then the thing to do is to make sure somebody else is there to keep an eye open during visits.
What were the reasons for its seeming like a good idea at the time to move your great aunt in with your grandmother? For companionship? - were they close in earlier years?