Zsa-Zsa used to get car sick EVERY time we got in the car.
I bought her a car seat and every day took her to the car and just put her in the seat and sat in the drive with her for a week for 10 min. Then we she tolerated that I would start the car - then drove around the block - then took a 30 min trip and finally she no longer gets car sick. It took some work but it was well worth it. She rides like a dream now.
Good luck