Well, she's had some bad expirances time to give her good ones. Plan a day when you can spend time just loading her. Then get her to load with out the stress of time or place to be. Do fun things with her such as graining, grooming, treats while she's up there. Then when you feal that she has come to some relaxation, take her off and put her away. Plan another day next week and do the same thing. If you spend all day so be it, show her that loading isn't about fear and rushing.

One thing I always use for a scared horse, is a long tooth curry or my fingers in a scok puppet position. and rub/scratch the horse where they would natuarally groom each other: Shoulders, neck, withers. Each horse has a spot that makes thier lips tighten or twich, this is the natural "mutral grooming" behavior, and is really good for relaxing a scared horse, and gaining thier trust.