What to do if a family friend tricked me into signing power of attorney of me over to her?

You can revoke a power of attorney by notifying all your creditors, banks, and other individuals or entities who had received the original notice.  In addition, you should send the revocation to the relatives and demand an accounting of all actions taken on your behelf.  If you live in Georgia, I am available to disucss this with you further. 

I do not know all of the circumstances surrounding your situation and do not practice law in your state.  Therefore, I can only give you general suggestions and not specific legal advice.

I suggest that you prepare a revocation document according to the laws of the state where you now live and the state in which the POA was signed.  I also suggest that you send a letter to your agent (the person named in the POA) saying something like this (change to words to fit your specific circumstances):  The POA in which you are named my agent, which was signed on _____________[date] is invalid because I did not understand what I was doing when I signed it and it was obtained under undue influence.  If you use this POA, you will be committing fraud or theft and I will take all actions available to me under the law.  To avoid any confusion about this, I have signed a revocation of this POA and enclose that revocation with this letter.

If you think this family friend will try to use the POA, you should give the revocation documents to all your banks, financial institutions, insurance companies, and others who hold or manage your assets.  If the "friend," tries to use the POA after receiving your letter and revocation, call the police.