I've dealt with RIs in three of my snakes (all came to me sick unfortunately) and from what you mentioned it could very well be the start of an RI. Impossible to say over the internet of course. If you can get a photo of the inside of the snake's mouth that would help a lot. When you peel down the side of her mouth is there lots of bubbles/mucus? Has she otherwise been acting the same or have you noticed her not being interested in food, leaning her head up against her enclosure/objects, or being lethargic/not flicking her tongue as much as normal?