If possible bring her car seat. Most kids "get" that car seat means staying put. Even if you didn't buy a seat, if you bring the seat to the gate you may be able to get the use of the seat next to you if you're lucky and the plane isn't full (if not they will gate-check the car seat.)
Other than that, I agree with the other suggestions. My kids weren't interested in TV at that age but I did fly with a 1yo (internationally) and we just brought bottles, snacks, and a variety of small things to play with. At that age I remember things that can go in and out of containers were big, so I might bring a little bag with crayons, stacking cups, that type of thing. Travel-size magnadoodle is good for a short time. My kids also liked having us draw pictures at their command ("now draw a dog").
Novelty is big - buy inexpensive little things you don't mind leaving behind so you don't have to carry them back.