While I can't promise anything, I find that even the freakiest settle after about an hour. Nonetheless, for pets like her, I'll often rescind my no-sedatives policy, using something easy like Xanax instead of the knock-em-out punch Acepromazine supplies.

But perhaps there's something you can try beforehand: desensitize her to the carrier. Leave the carrier out in sight of the food bowl. Inch it closer to her food bowl every day. Try inching it closer to her favorite spots where you can pet her. Use a pheromone spray (like Feliway) throughout the process (a diffuser of Feliway works great for some cats).

I know others will have their tips, too, so stay tuned.

Does she like the other cats? Are you going to have space for something larger than a single-cat carrier?

When we drove from Pennsylvania to California, I was worried about our cats. They cry all the time in the car on the way to the vet, so I was worried about 4 days of incessant yowling. I set up a large canvas dog crate (big enough for the both of them with room to spare) in the living room and desensitized them to it as Dr. Khuly recommends. Then I put it in the backseat of the car and put in cushions and catnip treats, plus a small bowl of frozen water.

They curled up with each other on the cushions and didn't make a peep the entire way. There was just enough room in the back seat for a Booda-dome type litterbox, and whenever we stopped for food and bathroom breaks I locked all the doors and let them out of the crate to use it, but they usually waited until we stopped for the night. I only offered food at night, in the pet-friendly hotel rooms, and they usually used the box before we loaded up again in the morning.

When I went to visit a "sanctuary" for cats in Maryland from NJ (was considering it for placement of a feral I have in my home)
I actually rescued a tiny little orange kitten from the sanctuary, and he cried for 4 hours straight on the way home. Now granted I didn't have time to desensitize, so anything else for that matter, but some cats are not good in cars.
I used to medicate one of my cats for the 2 hr drive into NYC to see the vet cardiologist, but finally stopped going because the trip wasn't worth the stress on the cat. Meds or no meds.

We're going to move about an hour from our current home in 9 months...I'm starting to prepare now, but I know it's going to be stressful ALL around....

My own three cats travel with us on vacation in a 5th-wheel travel trailer. For about a week prior to departure, they get short supervised visits in the trailer to explore, find the food/water dishes and litter boxes, and just generally to explore.They travel with lots of their favorite toys in air-conditioned comfort. Usually the only time they are stressed is the first couple hours, until they adjust to the movement of the trailer. The first day on the road, I ride in the trailer with them about half the time (not really legal, but hey, whatever it takes to make them feel at home--and I get to nap on the bed with them instead of dozing in the front seat of a truck)! By the second day, they are pretty much at home, and spend most of the time sleeping on the bed, the couch, or wherever they choose. They travel well, and I don't have to worry about finding a pet-sitter or kennel, which I think would cause them more stress, They have each other, and their staff (my husband and me) to see to their every need.