Katie-
I know how bad it sucks to have a cat pee on everything. It's embarassing, it stinks and it's just terrible. Perhaps you can borrow a cat condo or something from someone and put her in it for a week with litter box and food/water and kind of retrain her on using the litter box. You may have already tried this, but I know the rescue group I work with suggests this when people have problem pee'rs and I think it's worked pretty well. If not, I hope she can find a barn as a forever home instead of being put down.