inca was bad for being car sick, it was only after her first trip to the beach which was a 2 hour drive that she stopped.
how long into the car journy is she sick, does she cry at all before hand, where does she travel(frount/back seat or boot/trunk)
have you tried not feeding her.
if you have a drive way, take her out and sit in the car give her treats if you want, then take her back in. do that a couple of times then do the same but this time turn the engine on and sit for a bit, again repeat. them once she is ok with that, start moving the car, reverse the car out the drive then back in, and repeat a couple of times.
hope that helps.