The heaving could be a reverse sneeze if it looks like sides are going in and out and she's honking.
Reverse sneezes have the same cause as a regular sneeze but are much more dramatic!
You should look around the home for allergens and eliminate them if you can. Carpet powders, cleaners and pollen are pretty mean culprits.
I found an informative article that might explain it for you better than I can:
I have found evidence that the massage technique mentioned above works well as does forcing the dog to swallow.
Let me know if you still have questions.