I didn't read the whole thing (and saw that she got in, Yay!) but I had a similar experience with my mare.
Long story short, she had a bad experience and was terrified of trailers. We tried for hours and she ended up flipping over backwards.
We ended up sedating her with Dormosedan (sp?) and it worked like a charm. I highly recommend it for horses who won't load but you HAVE to get somewhere, like I did.
We have since retrained her and she now loads like a pro!
"There's nothing more humbling on the planet than horses." --Sean Crocker