I have always treated bee stings homeopathicall y and the swelling as subsided immediately with the proper remedy. My girl Skylar got stung this summer and since I was able to find the stinger and remove it, I also cleaned the area and applied calendula as well.
Given the facial swelling that is affecting her breathing however she would have already been at the ER if it were me. I don't mess with anything affecting the breathing like that and still can't forget the Golden I saw in the ER last year who had been stung by something and swelled up like a balloon - she ended up being hospitalized there for 8 days!!!
At this point, if you have had her home and things are getting better, not worse, than I would use a homeopathic remedy and watch her closely. If you aren't familiar with homeopathy you may want to read up on it for future issues.
Good luck