Why does your cat meow incessantly when she is in the car with you?

It depends on where you take the cat in the car. If you take it to the vet, it is going to meow in distress. If you take it to the pet store to get treats and such, its most likely to meow in happiness. Of course, the car and the idea of moving that fast are probably new to the cat, and especially if the cat is being driven in an area where its never or been very few times, its going to meow and yowl with a scared or startled look.