How much control does a person with POA have? My sister has it over my mom and several months after she got it she put my mom in a nursing home.

At first I agreed but then she moved her out of state and she lives in Montgomery and I live in Mobile. She has made it hard for my wife and me to see my mom and she hardly ever comes to visits. She has taken over everything my mom owns, from her house to her car, is she aloud to do that? She has been selling things off at least she says she has but I know my mom has income to pay her bills so I am not sure what is going on. I know at one time mama was paying all the bills at the house so my sister could stay in her house while she was visiting. Well my mom doesn't pay for my bills so I can visit an I wouldn't want her to and she doesn't supply me with a car or pay for my gas to visit her but she does my sister. Now my sister tells me she is selling my mom's house. Can she do all of this does it all belong to her. She told us her daddy worked to hard to let the state take it. He was my daddy to but my mamma is still alive. Isn't it her'?