Resignation of Power Of Attorney

Send her a resignation letter, return receipt requested, so that you have proof that she received the document. Unless you have specifically entered into a binding legal agreement to serve as attorney-in-fact for your friend for a specified period of time and you're getting paid for it--which would be the case if you were the trust department of a bank, for example, that performs this function professionally--you're not obligated to serve in this capacity any longer than you want to.  It would be a good idea to notify anyone who is counting on you playing that role that you're no longer doing so.  Also, although it is unlikely, in the event that the power of attorney is recorded anywhere, you should record your resignation letter as well to put the world on notice that you're no longer the attorney-in-fact.