Please know that not every horse responds to 'cookie cutter' training methods. I like to think of horses as intelligent creatures that can have a say in things.
Love that. So true.
We had some horses here awhile back that hated the front load as well. What we did for awhile, was back the trailer up to something, like the side of a barn, a hay stack, anything really. Have the back of the trailer be about 10-12 feet away, and block off one side. So basically you have a little box. Only way out is the way you came in, or into the trailer.
Any time your horse thinks about not being in the trailer, like looking away, backing up, or worse rearing, you have to do something unpleasant enough that the idea of getting into the trailer seems most pleasant. The moment she looks to the trailer, big reward
Having the trailer backed up against something gives a sense of security and also blocks from going backwards.
Little by little you pull the trailer out each time it gets easier, and pretty soon you've weaned her from the barricade. Do not lead her away from the trailer to re-align. She will straighten herself out if she plans on getting in the trailer. If she has no intention, get loud until she searches for the right answer. It's like black and white kind of clear. Trailer=peace, outside of trailer=no peace.