Werdna16...Sorry you are having this experience, and I'm sorry for the horse, too.
A seller can make all kinds of claims but obviously this one made a terrible mess of their horse, or someone did. Now you get to fix it. You know, I would have a vet check her out to make sure there are no physical problems and that the tack you are using fits, then start with Basic Ground Training 101. It will be a slow process to build her trust but with patience and consistancy, and knowledge, a lot can be accomplished.
Good luck to you and your new horse.
If you ever find yourself in a fair fight, it's because your tactics suck. ~ Marine 1SGT J. Reifinger