It is really hard to say what she is going through. All I can offer is this - about 3-4 days after deworming, I give a probiotic. I do this to repopulate their gut with healthy gut flora. Immune systems and digestive systems work closely together, so if you have a healthy gut, you have a healthy horse. The probiotic is cheap, comes in a paste and is easy to administer. Just a thought - good luck!