Thank you! I'll give that shot and see how it goes.
I don't know if she had a bad experience, though I shouldn't think so, she's only a year old. (Which also has something to do with being afraid of them) Her breeder's didn't handle her at all, then someone bought her and her mom but had too many horses and couldn't take care of them and sent then back to her breeder. Then I bought her, so there was some hauling involved. When we drive down the driveway (it's about 1/4 of a mile) she runs away, so I think it's the noise and movement like you said.