No, I can't bring in stone and make a dry lot. Since there is no way of knowing WHAT she's allergic to (it could be something in the trees) there's really no point in doing that, plus, I have no money to do that, plus, we are planning on selling the place soon and I want the grass there, not stone (It probably wouldn't be sold as a horse farm).
Unfortunately with chronic exsposure to whatever is causing the issue it's going to be a chronic battle. Dry lotting would be the best option for her to minimize exposure to irritants. Any hay fed should be given soaking in water.