I second ALL of the above suggestions, and would like to add a couple of tried-and-worthy suggestions for the "in case situations:"
1. Cola Syrup: while pregnant with my 2nd daughter, I experienced severe nausea AND had a trip to WDW planned. My OB prescribed a bottle of Cola Syrup (the base for, you guessed it, Cola sodas). However, it's not recommended for people with diabetes due to the sugar content. It worked for me to help curb nausea (if her motion sickness were to get "that far," this stuff is useful). OR, drink room-temp, flat Coca Cola if you can't get your hands on the syrup.
2. Eat a light meal no less than 30 minutes before take off & snack on those crackers (no-salt) throughout the flight. If she does experience motion sickness, her stomach will at least have substance in it, which will help if she has to {{T.M.I. time}} "upchuck." Her poor stomach won't feel all knotted from having nothing to squeeze out. Avoid greasy food and dairy products.
3. Prohibit reading, playing video games, and anything else that requires somewhat rapid eye movement. One of the causes of motion sickness is a sensory miscommunication; basically, an imbalance between what your ears hear and what your eyes see. If those two senses are on overload, and/or if you have an inner ear problem, and/or if you are more easily prone to nausea and vomiting, your risk for motion sickness is greater. A SOLUTION: sit in the front of the car, plane, ship, and keep your eyes focused on the horizon (or a sedentary object in front of you).
4. Take ginger BEFORE, DURING and AFTER the flight. Ginger is a natural remedy for "settling" the stomach (but beware, the carbonated bubbles in ginger ale or any soda can actually make things worse if your daughter is already experiencing motion sickness).
5. Benadryl is an alternative to Dramamine.
6. I know it sounds funny, but look up "Pregnancy Lollipops." They can curb the nausea.
I hope this helps a little!