OK. These are good ideas. I can't leave trailer out long-term, unfortunately, so I may have to try the two methods combined--gradual desensitization and food, glorious food.

I really am sick about this. She's a good little mare who we upgraded last year. She's been through hell, and she's our first horse. I know we're in over our heads most days, but what can you do? I can't sell her now. She's a big pile of issues, and I wouldn't trust someone not to send her to kill.