Anxiety meds for dogs

We have a very anxious little rescue dog, she’s happy and carefree around me and my husband but is terrified of anyone else and car rides We’re going on a family vacation and are bringing her with us. Can you suggest any supplements or medication from a vet that calms dogs in high stress situations? I don’t want her to be miserable the whole time but we’ve also tried dog sitters before and it failed miserably so we can’t leave her either.