That's adorable. Try to not feed her or give her too much water before the trip. She can eat and drink when she gets there and it won't hurt her.
You can also give one Benedryl tab and that has anti emetic as well as calming effects.
That said, we once had a German Shepherd/Border Collie that managed to throw up in the car every time no matter what we did. It was unbelievable. Some dogs are just that way.
You could crate her and then you only have to bathe the dog and clean the crate instead of ruining your car interior.