Olive oil and mineral oil work well too..they're thicker than vegetable oil and seem to work faster.
Does she have any discharge from her eyes/nose? Is she sneezing? Lethargic?
A few months ago, one of my lop does had a bad breathing issue that sounds similar to your doe...raspy heavy breathing that sort of sounds like a pig. She had no discharge and no other symptoms and after some research it seemed like the problem was caused by the heat/humidity...apparently when rabbits breathe heavier and faster, they can easily wear out the mucus in their throat and nose and after a while it causes raspy breathing. She had a litter of kits at the time and none of them showed any signs of it so I knew it wasn't contagious.
It took about a month before she started breathing normally again, I put some 'breathe easy' essential oil on the bars of her cage and that helped a lot, and I put some echinacea tea in her water bottle. I hope your doe will be alright.