If there was no living will how do we know who gets POA?

I'm sad to say that my cousin had passed away the hospital gave my aunt amd uncle power of attorney for medical reasons they want to sell her house to help pay for arangments and medical bills. The problem is both her mom and dad have passed away and she has no brothers/sisters just aunts uncles and cousins. She had taken in a no good junkie cousin who is saying she has POA because she is paying the bills atthe house. If there is any way to find out please let me no. Thank you in advance.