If your mother is currently incapable of making medical and financial decisions, she cannot give you a power of attorney: only a person competent of managing her own affairs can create a POA. If your father is neglecting her interests, you may have to consider trying to get her declared incompetent by the courts and have someone other than your father appointed her guardian. This is a drastic step, and is apt to be difficult--courts do NOT like interfering in a married couple's internal affairs, or taking away spouse 1's rights or authority vis-a-vis spouse 2 when there is any other option. You may wish to discuss the situation at length with an elder law attorney, but be prepared that there may not be a good answer or resolution for you.