It has been a while since I played the cancellation game. There may not be a risk free way to do what you want. The least risk would be to ensure the AA number is only in one of the bookings, and I believe (but can't guarantee) AA will not cancel the CLT-MCO leg as long as it departs after the initially ticketed CLT-MIA leg. I am much more confident they will not cancel the CLT-MCO if it is scheduled to depart after the CLT-MIA is scheduled to land, but that gives a fairly long layover in CLT. It may be possible to book the CLT-MCO leg late enough to not interfere with the CLT-MIA leg, and then try to standby for an earlier flight if available, but she would have to give her AA number to do this for free. I'd suggest only doing this at the gate of the departing flight and not earlier. If possible try to have your niece's name spelled differently in the bookings (Jen and Jennifer, Sue and Susan, that kind of thing). Keep the boarding pass and submit for credit after the flight. MIA-MCO is pretty cheap too, with many flights under $75 or 5,000 miles, and who knows, with a schedule change on any of the flights, she may be able to re-book for what she really wants. Best ideas that I can come up with! Good luck!