Do you every notice mucus comming out of the sides of her mouth? My first thought would be some sort of RI as well, the other thought is (and this would just be a guess) open her mouth and see if something like a piece of aspen is caught in the back of her mouth/throat. My buelys huff all the time, but that is completly different than hacking. Personally if nothing is caught in her throat I would take it to a vet just to be safe.