I would try crate training!
If a dog thinks that a crate is there safe place, the crate could be anywhere and they will still go to it for comfort. My pup is only 10 weeks old, but they pups were kept in a crate and so she goes to this one all of the time!
Desensitization is key too. Take them in the car, then get out. Take them for short rides, then get out. Make sure they are comfortable!
It's an inconvenience to some, but most people don't understand that behavior is also a responsibility that the owner has to help and fix/maintain.
Sounds like anxiety and probable motion sickness to me too.
Get some Ginger Snaps and feed her (not sure of the size) one or two before going in the car. Try getting her used to the car by taking short trips (10-15 mins). It us better if she can see out, face forward and have fresh air. Don't make a big deal out of it. Praise when you get back and reward. Gradually work up to longer periods of time. You could even start by just going down the block and back. This may take a while. Maybe take her favorite blanket or a toy with you.
If that doesn't work, like Karla said, you may need something from the Vet or Dramamine (check with the appropriate dose)
If she is drooling in the car, get a baby bib and put it around her neck, just get one that is an appropriate size and she won't step on.
Welcome....I'm unsure about Gaba's safety for such a small dog.....Plus, it would have to build up for effectiveness....However, everything you have tried is for anxiety...This sounds more like nausea (Motion sickness) to me...Ask your Vet for a few small doses of an Anti-nausea medication for your trip.....Karla