She is 52 years old and live with my mom but my mom is getting old and can not take care of her.

You may wish to go the guardianship route instead which is much easier to do. See any family law attorney to help you draw up the appropriate paperwork.

Who currently has custody and poa (power of attorney) over her affairs ?

As long as your mom agrees, * assuming your mom has custody or guardianship though the courts.

I will say that unless her health is poor, 52 is far from old, and a active 52 year old in good health would have no issue caring for anyone.

I will say that unless her health is poor, 52 is far from old, and a active 52 year old in good health would have no issue caring for anyone.

Chuck, I believe the disabled sister is 52, not the mother caring for her. I may be wrong, but that's how I read the question.