First, the statute of limitations in RI for suits based on contract is 10 years (see RIGL 9-1-13 here http://www.rilin.state.ri.us/Statutes/TITLE9/9-1/9-1-13.HTM).
Second, the question seems to state that she loaned you money, in return for which you signed some document - presumably something acknowledging the loan and agreement to repay. Later she verbally stated that you need not repay the loan - she would forgive the loan. And most recently she has demanded payment.
A court could conceivably believe that you mom did forgive the loan, in which case you would not have to pay her.
But the right thing to do, IMHO, may well be to repay your mom regardless of anything she may have stated later. After all, she did loan you the money, presumably at a time when you needed it. And she has bestowed many other gifts upon you, including the invaluable gift of life.
Note: The above information does not constitute legal advice. Unless a written Collaborative Representation Agreement has been signed, neither LawyersCollaborative nor any of its Staff General Counsel is your legal representative.