Can My father's dead wife's daughter control my father because she felt that part of estate should goes to her?

Well if his wife had no Will, state law for "intestate" (no Will found) apply. In New York, the spouse does not get everything. We went through this with Dad. No Will would mean his wife got 2/3 and his children (us) got 1/3. NY has a waiting period of 7 months, so the court appointed fiduciary has to wait 7 months for bills to come in, then distribute the estate.

POA's don't have the authority to decisions and distribute property to themselves or others on their own agenda. They have a fiduciary duty to handle the person's property, funds, assets for the benefit of that person, not themselves. I would question if they are taking funds or property for themselves. I'd consult with an attorney to explore my remedies. Also, how the funds and property are handled may be provided in some jurisdictions with the Clerk of Court. Unless the POA document waives it, the POA may be required to file an annual accounting showing where every dime went and why.

Your father gave his step-daughter POA and medical proxy, right? (https://www.agingcare.com/questions/can-step-dads-daughter-have-power-of-attorney-over-my-mom-197077.htm ) That does give her some authority, but not "control" over him.

NO. It is very common for the wife to leave everything to her husband. What he does with it is up to him. Nobody else.