Starting with short trips and gradually making them longer as she adjusts is good advise. It's always wise to not feed of water for some time before an anticipated ride as well. If there's nothing in the tummy, then they are less likely to be nauseaus. Did you know that Dramamine or Bonine can be given to lessen car sickness? You should call your vet (have your dog's weight handy) for a proper dosage. Many dogs do outgrow it, though some take longer than others. Good luck!