Hi my wife just passed away on the 13rh of June and she got out of the hospital and passed the next day her nephew popped up with a power of attorney

I'm very sorry for your loss.  A power of attorney gives an agent the power to act for a living person.  it has no effect after death.  The power to act on behalf of your wife's estate would be determined by her will and by the court in a probate proceeding or, if there is no will, by the court in an administration proceeding (those are the names in NY, they might be different in Dalaware, but whatever these proceedings are called, they will determine who can act on behalf of your wife's estate, not a power of attorney).