I prefer the softsided carriers to the hard bigger carriers for a couple of reason. first off, they are cozier for a cat and have the feel of a secure environment. they also usually have a side and a top zipper so it is easier to get them in. You might also try putting in a blanket that she sleeps on so she has her scent already in there and it doesn't smell like the other cat, or a shirt (unwashed) that you wear. I leave my carrier on my bed a couple of days before so my cat can inspect and rub her scent on it. Make sure the room you are putting her in has some familiar furniture or toys so she immediately has the smell like home. I also suggest that you unzip the carrier and let her come out on her own, she may not like the carrier but it will be a familiar hideout in a new place. When I move, my cats are the last thing to go so they move from one room to the new without any stops in between.
I also caution you about medication, while it has some benefits it can also make a cat stress more. My cat was on Kitty prozac when I moved cross country but became very dehydrated and stopped eating. the medicine reacted badly for her and after two days on it, I took her off and she seemed to get her travel legs back as well as her appetite. I realize that your trip is much shorter, but talk to your vet about side affects and see if its worth it to move such a short distance. you might be better off just putting up with the cat for the short ride.