sister takes moms house

I come from a family of 5 siblings. My mom put her family to rest after making an extensive move 12 hours away. My moms parents were bed riden for some time. When her parents past 5mo apart she was then left a home car several thousands of dollars of assets,and several cd acounts worth 100's of thousands. My grown sister moved into moms inharited home with her 2 sons, she had never married. Her plan was to build onto the historical home changing it and getting her name on the deed of the home as though it was hers. Mom accomidated her by letting this happen. The rest of the siblings were notified later. Since then mom has paid the
majority of the now mortgage on the house.
Sister also paid off several things with this loan on the house like a car, cr cards,and other investments for her future.
NNNooooowwwww as you were to guess she accomplished her goal in just a few years
she wants out out of the house away from mom.
She is planning to sell the house. Mom is not logical she thinks we should be happy for what our sister gets out of the deal and that
we the rest of us will take care of her and put a roof over her head and put her in a new
car. Her money she inharited is down to 1000
dollars a month. The rest has been frivalousely spent, given, lost, and what ever she gets out of the sell of the house
we dont expect to much. Is there anything leagal we siblings can do about this before it happens.??