The best place if motion sickness might be an issue is wing seats, it's the most stable part of the plane in flight. Gum is the best thing for your ears when the pressure changes occur, can be quite painful for some. You'll want an aisle seat, I'll bet she'll want a window seat, lol. Remember to get up and walk around some in-flight to help circulation, and the recycled air on planes can be very drying. As for bringing your own snacks, you have to check with the airline, some allow it, some don't. Wear shoes you can slip on and off easy, I'm not sure if you have to take them off if you're using the new body scanners, but I know you do now for the regular metal detector. A friend of mine flew recently and her daughter is autistic, she brought paperwork with the diagnosis from the doctor because her daughter can't do the standing still with your arms over your head for the scanner thing, so they got whisked through on the old metal detectors and jumped to the front of most lines.