Rosie, I have HORRIBLE ear pain when flying. Buy
SUDAFED (tiny red pills) from the pharmacy,
NOT over the counter as it is not the same. You can ask for the store brand as it is less $. It is a decongestant. I also take bendryl, but most people do not need that much. You will have to sign for it and show an ID b/c only so many can bought every 30 days (the girls could not pick it up as they are under age).
How long is your flight? If more than 3 hours, then she will need to take 2 two hours before the flight and 2 again an hour before it is time for decent. You take them every 4 hours, so if your flight is like 3 hrs and 45 mins, taking them once will not help.
Personally, I cannot use a nasal spray (makes me gag), but she could call her Dr and ask if s/he could give her a prescription for a decongestant nasal spray if she prefers that to the pill.
The ear plugs do nothing for me - I think they work for people with mild ear discomfort. You can buy those at the pharmacy too.

She could take both.