Is it necessary to change POA over my mother from my step father with terminal cancer, to me her daughter?

My step father currently has medical and financial POA over my Mother (in an alzheimers care home currently), they have been married for over 35 years, and lived in CA. He moved to his home state of Kansas within 3 months of moving my Mother to a care home in CA. I live in NV and my brother lives in AZ. My step father is terminally ill with lung cancer and has very little to live, I want to make sure my Mother is taken care of for the rest of her life, they have marital assets and she receives social security as well as a retirement pension.