I looked at your location; it can't be that long of a flight to MCO, can it? Is the flight hitting her nap time?
We used the convertible seat for awhile, but when one day our flight was cancelled when we were at the gate and we were shunted to a nearly full flight and I just couldn't handle the idea of installing the roundabout and gate checked instead, my son did soooooo well with just the seatbelt I wished I'd done that the year before. Now, he was already 2, not nearing 2, so that's different, but he did really well. And that was a west coast flight, similar to your east coast flight.
My son fought the carseat all the time, but seemed to really understand that the seatbelt was going to be ON, and that he needed to be a big boy or the next flight we'd bring the convertible again. He rose to my expectation, much to my surprise.