Sorry...didn't read all of your posts so I may be being redundant. Good instincts about the meds. I would never recommend giving your child medication unless it warrants it. Anything that makes her jaw move (a drink-purchase AFTER security), a lollipop or some chewy candy, preferably gum will help with pressure. Make sure she didn't put a juice box in her back pack, as it will be confiscated.
It's great that she is packing her own airplane backpack. A deck of playing cards is good. My kids love to do this - I would sometimes sneak a surprise toy, new beanie baby or coloring book in there, just for fun. Having her own dvd or music is good, however, I would not have any toy with a repetitive sound. It's annoying to listen to. Also, if she DOES bring in her own music, sometimes people have a tendency to repetitively kick the seat in front of them to the beat of the music, so just be aware that this could be happening- just had this happen with a grown man, behind me, on a flight back from California. Arrrrrggghhhh!
Make sure you tell the flight attendant that it is her first flight as they may have little flying pins and possibly coloring books for her, depending on the airline.
Don't know if you would be flying Southwest Airlines at all, just a thought if you are: Remember to check-in on-line, EXACTLY 24 hours in advance - on the minute, on your home computer. They will prompt you for the person's name and ticket number. This way, you will get a better boarding position.
Also, since she is young, I implemented the game with my kids at that age and the rule applies now. It's called the "No talking game". Since my kids had/have flown pre and post 9/11, it became important for them NOT to ask any questions, through x-ray and security that could be potentially misconstrued. ... So, once we get to security and x-ray, we'd "locked our mouths" and could only hand gesture or nod. As soon as the "shoes were back on the feet" the kids started talking. I feared that a simple question could get us delayed - I've seen a lot.
It's funny. From my daughter's first flight, when she was three, we have held hands, just before take-off (she usually is across the aisle from me now). It's tradition. We gently squeeze hands until the plane is comfortably in the air. I used to do it to make sure that she was not scared. Now... it's just a nice tradition.
Here's to making traditions of your own!
Have fun.