It sounds like its a gut acidity problem. If she cribbs (i assume you mean she 'gulps' air down) she could be colicing from filling herself up with air, or not maintaining a constant flow of food through the stomach. Horses draw air through the gullet like this to produce endorphins which mask pain caused by a too lower pH in the stomach.
Try adding a probiotic and prebitoic supplement to the feed. It can soothe the acid and helps the function of microbes in the gut. Probiotics add microbes, prebiotics give the 'good' gut microbes nutrition so they can out compete the 'bad' microbes. I don't know about america, but here in britan NAF, spillers and blue chip products are pretty well know for this kind of thing
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