I really feel for her, I have been proper grown-up for many years and still suffer – it’s my Kryptonite, I can’t event watch the Onedin Line and have to look away when they put cameras on the front of the F1 cars.
What works:
Dramamine or Promethazine Theoclate, in double the recommended dosage. This has the added advantage of making you drowsy. Boots own brand tablets or Avomine are effective.
Combine this with a good view out the front of the car, and a cool blast of air to the face.
I would also politely suggest that you assess your driving style and keep it smooth. Hilly corners are the worst, travel sickness is also caused by acceleration/decceleration so if you are the kind of person that brakes into corners and speeds up out of them you are contributing to the problem.
Also, driving close to the car in front and stamping on the brakes guaranteed to make me puke.
Those wrist things are just the placebo effect. I SO wanted those to work. No good.
But the BEST thing for it is sleeping pills, again twice or more the suggested dose I have got through some very dodgy flights heavily medicated, though that possibly isn’t an option for a child !!