Phebe's mysterious mouth swelling.

It is always something...her scratches are clear on three legs now, and the last little spot is about the size of my little fingernail on her left hind pastern. She is taking an antifungal drug orally, and furazone topically which between the two has about got it whipped. I was ready to heave a great sigh of relief that I would not be doctoring a horse for the first time in three and half months. Then the middle of last week I saw her jaw was very swollen just below the ridge of the cheekbone. It was very hard and didn't seem to bother her when I pressed on it. A couple days later it was gone. This afternoon it was back again, even bigger. I could just see the rodeo of getting the vet out here, the footing slick, Phebes freaking out because she hates the vet. So I trudge back in the house thinking if it isn't better tomorrow I guess I'll have to suck it up and call the vet. I go out an hour later to catch her to treat her pastern, go to put the halter on and she looks perfectly normal! Is the little bugger getting a wad in her jaw eating??? A dental swelling can't just pop up and down in a matter of an hour? If it pops up again I'm going to stick my fingers in there and see what's up...