The only way to keep her symptom free is keep her away from roundbales, like, yesterday, in fact, as of now, the only way she can have hay is wet, or maybe, if it's good quality hay, in a slowfeeder haynet, where she cannot bury her nose in, has to take a strand at a time...which, in turn, would also help with her weight.
If you can't get that at the place you board, find another place.
The Ventipulmin Cherie mentioned didn't do a thing for my heavy mare. I've seen others where it did wonders. It is pricey.
Have you consulted a vet?