there are child size earplugs called earplanes. very comfy and help a lot during takeoff and landing. also lollipop. wouldn't give her medicine, could have the total reverse effect from what you want.
take medication with you while on the trip, motrin, tylenol, claritin, benadryl, triaminic etc. you never know what you'll find there. also make sure you have plenty of snacks on the plane, a drawing board, maybe a dvd player with a few of her favorite cartoons. don't freak out. there are pickpocketers everywhere, goping for pockets and purses, therefore i recommend one of those around the waist money belts to put in your passports and cash that you might have. don't leave passports and tix in a hotel room. make sure you make copies of passports and tix and leave copies with someone whom you have fast access to in the states if needed (faster getting passports through the embassy in case yours gets stolen-
good luck
vlora