Can the POA of my mom sue me for inheriting dad's money

Sure. In order for my step mom to receive Medicaid we needed to remove her from my dad's assets as co-owner and make me the beneficiary so if he died before her Medicaid wouldn't deny her benefits. She is bed ridden with end stage dementia. My dad had died and his assets went to me as the beneficiary. My stepmom's sister is the POA and although we, my sister and I, have been paying all the bills, her sister has done some underhanded things and is trying to get the money from me. Can she do that?