Isabelle had quite a few uti's when she was a pup. She too never had accidents unless there was an infection. I don't recall anything ever being mentioned about her vulva. She was spayed around 6 months. She never had a heat cycle. She also drips. Luckily the drips are controlled by meds. that are chewable

makes it easier. She sits for her medicine. It's kinda funny - you tell her time for your medicine and she runs to the kitchen & sits. I agree with Velmadobe about waiting for a heat cycle - it may fix itself. Good Luck & I hope she's felling better.
Oh - Did they test her unrine to make sure the infection isn't in her bladder?