Gotta say that kitty valium works wonders for long road trips for kitty. It helps to mellow them out so they are not over flooded with anxiety. I moved my cat from California to Arkansas, and the trip took three or four days (only drove at night due to an old car and not wanting to overheat it). By the third day, she didn't need the pills anymore and had adjusted on her own.
You may feel uncomfortable about dosing her for a road trip, but it might be better for her in the long run, and better for you. She doesnt torment herself with stress, and the driver can stay focused on the road a lot easier.