Is it possible to park a trailer where she can get in and out of it on her own, if so put some feed and water in it, and see if she will go in on her own. We had one that was scary to load, and that is what we did. He had hay and water outside, but if he wanted his grain or treats, he had to go into the trailer to get them. It took a couple of weeks, but he got used to getting food there, and he was much easier to load, not great but better and safer. I used a stock trailer for this. It became his barn all summer.

Edited to add
Make sure the trailer is secure and on either blocks or something at the back corners to keep it from tipping when the horse walks on and off.

http://standardbredhorses.yuku.com
Last Edited By: Louise Mar 14 08 3:38 PM. Edited 1 times.