I hope the exam goes well! I don't know about genital myco, but I believe with polyps the treatment is a spay.
I've had 2 girls with vaginal bleeding before. 1 girl it was a disaster. this was my terminator that made it to 2 1/2 though against all odds
so there's hope! with her, she started bleeding on a Thursday and by Sunday (after an exam and everything) she was going septic, despite being on meds. fluids helped and after some ER vet disaster stuff, my girl went in for a spay with my vet. they found abnormalities in a uterine horn, which was likely part of the problem. which may be what your vet is referring to when saying there can be other things involved like the polyps, etc.
my second girl, I don't remember if they found anything abnormal with the uterus. she started bleeding lightly, we thought it had gone away, then it started again about a week later so we had her spayed.
my vet basically treats with antibiotics to stabilize and control infection as much as possible, but spays to fully treat the problem.
I'm not sure this was much help. I really understand with the cost of spays. they're about $150 for me, but depending on the reason for the surgery the cost can go up. it's expensive