Managing travel sickness?

Hey all,

We have a ~5mnth old Standard Dachshund. We're trying to get her used to car journeys as we have family that are 3+ hours away and also would just like to take her further afield.

We thought the travel sickness at first would just be down to being such a small baby and never being in the car before, but it's every time we go anywhere in the car, like not even 10 minutes into town.

The more she is sick, the more anxious she gets about the car. We've tried travel sickness tablets and we will usually avoid feeding her before travel, opting instead for a larger meal later in the day. She is usually better if she is being held, but UK law says dogs must be suitably restrained so we really want to get away from doing that. We have a pet car seat but she keeps trying to fight her way out of it, and her anxiety in the car just seems so much worse while she's in the car seat, even if i sit next to her in the back.

Does anyone have any tips for getting her used to the car more? We're trying to do shorter trips in the car with her but even 5-10 minutes usually results in throwing up. TIA!