While I understand it is a stressful situation, as long as the person who is travelling is on 1 through ticket (RDU to London), they will be looked after. The RDU agents will be focused on getting that flight away, so tell the traveller to relax, travel to New York and the agents there will get them on the next flight to London (this evening sadly if they miss the only day flight operating) or they may be paged when they land at JFK and handed their new boarding pass. It has happened twice to me and AA were very proactive.

Pilot37