I fully believe that she could be worth that much to the right person (I have been looking around a couple of different sites at other barrel horses for sale... Wow). I'm not sure I'm wanting to sell her though; my little girl loves her, and I'm pretty fond of her myself. If you're on the ground, she's a doll, it's just trying to ride her that causes issues. I guess if that is what she really likes and wants to do, it isn't fair for me to completely take her out of it, but I'd like to think there could be a happy medium.
On one hand, I agree with Kevin and Cori, that she would likely make someone a very nice barrel horse and make you a very pretty penny. But if you are determined to keep her, I like the idea of some down time and then bringing her back up from the start. Even after you get back into the saddle, do nothing but slow work; walk, jog, controlled lope and all of it on a loose rein. We already know she's good at fast work so that's not what needs fixed, it's her slow work that's lacking.