Answer:

Before your actual car trip, spend some time getting Molly accustomed to riding in the car. Gently place her in a carrier and take her on short drives around the block. These very short outings will help her get comfortable with the motion of the vehicle without it lasting long enough to cause much anxiety. After each training session, give her a treat if she's motivated by food, or conduct a fun play session with her. Gradually increase the travel distance every few sessions.

When you do take the long trip, bring a light sheet with you to cover the carrier if Molly hyperventilates (often it's the sight of the scenery whizzing by that disorients a cat). You should also line the carrier with a towel in case she has an accident. Bring extra towels as well so you can reline the carrier with a fresh one if needed. Don't forget a plastic bag for the soiled towels.