I read through the entire thing. Part-way through, I wondered if it wouldn't be wise to ask Mom if
she was cared for well by Sis. If it was okay with Mom, then Sis could have stayed on to care
for her. I finished the read and knew Sis staying there was a bad idea. Good for you all to tell
her like it is.
Sis would have drained Mom's money, leaving nothing for her care, she would have tried to
get a reverse mortgage or ownership of the house. Even short of that, she would have cared
for Mom until Mom died, then expected the entire house, regardless of what the will said. She
would have said "I lived here for years caring for Mom, you can't kick me out." Even if she didn't
get you all to turn the house over, she would have wanted you to allow her to live there rent-free,
meaning you can't sell the house. Who knows how far she might have (or even might still) gone.
You told her what's what. Stand firm. Tell her the local elders or the state might be of some
assistance. You might need to discuss things with a lawyer, since she's in the house. You or
your brother need to seize her assets for a trust fund or something to pay her bills, perhaps.
Don't let Sis pay the bills, and mix her own into the shuffle.