Power of attorney?

my mum has power of attorney for her mother, recently aunt has been asking questions as to my grans current monetery afairs (shares and bonds inluded)as to calculate her estate in the will.my mum didn't even know gran had any, my grandmother is not yet incapable of managing her affairs. my mother is worried that my aunt may be making moves to some how corner the estate (she has already removed two grandchildren from the will and convinced my gran to exclude two great grandchildren from the will). my biggest worry is that she could cause my mum to either lose her POA or be fined or removed as POA.my aunt has allready made my gran change bank accounts, is their anything she can do to hurt my mum,as in make out my mum changed banks etc. not being bitter towards my aunt but she has already contested my uncles will a few years ago.