4 year old horses

My 4 year old fjord loves trailers. To her they are fine restaurants and fun places to go, at least if they aren't moving. When she was little, I trained her to go in a trailer by tapping her behind. Eventually she loved trailers so much I didn't worry about loading her. She just went in. There is often food there. But I didn't take her very many places and driving made her so nervous she ended up dripping sweat. I recently had to take her to a saddle fitting clinic about an hour and a half drive away. We did a short trial run with her a few days before and she ended up dripping wet. Then I decided to get her a mild tranquilizer from the vet.