Look what you are describing is sheer panic! So do not hit her or give her Benadryl (can be toxic for cats!!!!) Really, never smack your cat.
My advice call your vet or an emergency vet visit if needed (mobile vet if you can.) You should explain your cat’s sheer panic and that she is a danger to herself (& you) in the car. Ask if you can pick up a sedative for her that will knock her out for the car ride when you move (& if you are moving far away ask for her medical records to.) Be sure to ask for enough for you to get there plus some extra if your trip takes longer for whatever reason.
I have never had a cat panic that much in a car. The closest I came was my boy hyperventilating in his crate on the way to the vet. So my mom drove and he was on my lap in his crate with the top zipped open. I pet him and comforted him. He was fine. My teen kitten now? He goes on lots of car rides and is used to it. I just hold him and pet him softly the whole ride. I also take away his wet food 3 hours before and dry food 1 hour before (you may not be able to do this when giving the much needed sedative.) That way he doesn’t get carsick. I also encourage him to use the litter box by cleaning it right before I go so he won’t have to pee during his 30-45 minute ride.
My advice call your vet or an emergency vet visit if needed (mobile vet if you can.) You should explain your cat’s sheer panic and that she is a danger to herself (& you) in the car. Ask if you can pick up a sedative for her that will knock her out for the car ride when you move (& if you are moving far away ask for her medical records to.) Be sure to ask for enough for you to get there plus some extra if your trip takes longer for whatever reason.
I have never had a cat panic that much in a car. The closest I came was my boy hyperventilating in his crate on the way to the vet. So my mom drove and he was on my lap in his crate with the top zipped open. I pet him and comforted him. He was fine. My teen kitten now? He goes on lots of car rides and is used to it. I just hold him and pet him softly the whole ride. I also take away his wet food 3 hours before and dry food 1 hour before (you may not be able to do this when giving the much needed sedative.) That way he doesn’t get carsick. I also encourage him to use the litter box by cleaning it right before I go so he won’t have to pee during his 30-45 minute ride.