That doesn't sound like mouth rot to me, but I have not seen it in person either. My guess is that the blood was from you opening her mouth as you mentioned... usually, what I hear from breeders is, unless there's a reason to open the mouth - don't. If you've noticed darkened gums near the opening of the mouth (more outside the mouth) or noticed anything off when the snake yawned, that's about the time I'd be opening up the snakes mouth.
Pinkish colour is a good thing. Does your snake wheeze only while in shed? If so, could be the skin around the nostrils as again you've mentioned. If anything, the bubbles might be more indicative of early respiratory infection, if coupled with wheezing (while not only in shed).
Personally I don't rush off to the vet if something is "off" in my mind, because more often than not (in my case, every time so far) I am wrong and there's nothing going on. Doesn't mean it's always going to be this way of course! Precautions are always good to take.
However, maybe that's just me, but I don't have the time or money to do that every time I am in doubt about something. Not to mention, there's about one exotic pet vet around my area, and I have not heard any reviews whatsoever on her/him. I'd be more inclined to ask a seasoned breeder and experienced handler before running to the vets. They can usually assist with things like opening mouths, and may be able to tell you exactly what's going on and what medication, if any, should be used (from experience or that sort of thing). That is when I'd hit up the vet for a prescription.
Just how I'd do it.
All the best!