even though Dunking is a pain , makes the water nasty fast, some horses insist on doing this. I would wet the grain when you feed it, don't have to saturate it, just wet it some. I agree to have her checked for ulcers and teeth problems.
Darn, I wished drinking water after I eat, or while I eat would wash the food through me !! I drink a 16 oz bottle of water before I eat, and drink one while eating , and I don't lose weight.. ;) Now if a horse wont eat and just drinks, I would say you have a colic .