How to deal with problems with a sister?

Our sister taking care of our Mother in Puerto Rico is demanding that we pay her for the care that she provides. In the meantime our sister is receiving our mother’s Social Security checks, rent from our mother’s house, food stamps. She keeps telling us that the money is not enough to hire someone to stay with our mother for a couple of hours. Our Mother is immovable, doesn’t speak, has a feeding tube (I didn’t agree to). My sister makes all the decisions for our mother as I live in the States, our only brother also lives in PR he tries to help by visiting or stays with our mother for a couple of hours. My mother stayed with us for 6 months (Hurricane Maria) and I didn’t request anything from anybody. Before sending our mother back I asked our sister if it was ok as our mother already required a lot of care. After going back our mother had two falls broke a wrist and then fell and broke her hip. Since then she doesn’t get up from the bed. We try to visit as often as we can. My brother and I are talking about transferring our mother to a NH if the problems with our sister continues.