Chronic urogenital infection - help?

I have a 14 month old standard poodle, had her from a puppy. From a young age (well before spaying) she exhibited some submissive urination, but we've dealt with that and I consider her housebroken, though she does still pee a bit when she is excited or (rarely) scolded.

Even before she was spayed, she tended to lick her genitals to the point of getting reddened skin down there, although for a long time that was the only symptom - no redness inside the vulva or anything untoward-looking. Vet put her on antibiotics a couple of times without much effect. Vet speculated she might grow out of it. Urinalysis showed white cells, but that vet didn't offer to do a culture.

In December we boarded her for 11 days. After that, she DID exhibit swelling and redness around her vulva, AND (this is the worst) a yellowish-green discharge. Some licking as well, but no extra urination, no peeing in her crate, anything like that.

I took her to a specialist since the other vet didn't seem all that interested in finding the problem. This specialist examined her physically and didn't think her anatomy looked too tucked-up (which I understand can contribute to these sorts of problems). Did a sterile urine culture, which showed it was not a kidney problem. Another urinalysis found 2 bacteria that were not out of the ordinary. Put her on an extremely high dose of Clavamox for 3 weeks. Not much change. Did a ultrasound, nothing out of the ordinary there. (This proved that it wasn't a pyro-something problem due to the spay.)

At this point I have spent about $1000. The next thing they can do is an endoscopy, where she has to be anesthetized and they put a tube up there to see if she has some physical object up there, like a burr or stone, that could be causing this. (We do live in the mountains and she occasionally runs through areas that have lots of stickers and such.). The vet has seen this kind of situation, though rarely. Cost is around $800, plus the risk of anesthesia etc.

I'm torn as to what to do. This dog exhibits no signs of being in pain or discomfort, just an occasional licking (which no longer causes a dermatitis). But seeing this greenish-yellow discharge coming out of her is very distressing. Specialist vet says it "probably" isn't causing her harm to let this go on, as long as she's not in pain. Can this be true?? I just don't know what to do. Would love some opinions from you all!

Nele