E.N.
I made this exact trip with my son over Christmas - he was 11 months old and I had to go alone. We flew into Atlanta and then drove to Athens (about 2 hours away). The truth is, letting my son walk in the terminal to his heart's content was so stimulating that he slept the entire flight to Atlanta. This is his 6th time on a plane, and it happens every time. Keeping him stimulated and entertained in the terminal before the flight inevitably causes him to sleep for at least 2 to 2 1/2 hours. The car ride was a little tougher, since he'd already slept we just had to keep stopping and getting out with him.
Before we left, we took him to the toy store and had him pick out a couple toys that he really liked (in this case, books that made noise and sang to him). He didn't get them until we were on the trip, and they worked perfectly.
Definitely brings snacks she likes - and something to drink (my son was still nursing, but the point is you want them to swallow to clear their ears).
A bulkhead seat offers a lot more room, but you also have no place to store any bags during takeoff and landing with that seat, so you'll have to put that overhead and then retrieve it.
I agree with the diaper change - it's basically impossible to change a diaper on a plane. Very hard and just not fun.
Focus on your family and your daughter, don't worry about anyone else. They may not like it if she fusses, but it's only 2 hours and not the end of the world.
Good luck!