So sorry for what your friend is going through. I can totally relate.
GRRRRRRRRRRR that is so frustrating! When I was 19, I bled for 3 weeks and had horrible RLQ pain (not low enough to be appendicitis). My family doc said "Sounds like you have an ovarian cyst, we'll wait for it to go away on its own." Told me to take Advil and sent me on my merry way.
The cyst came back off and on for the next couple years; I saw an OB who ordered an ultrasound which showed a 3X4 cm. cyst on my left ovary; when I pointed out the pain was on the right they told me that sometimes it can radiate.
Anyway, the upshot of this whole story is nobody ever figured out what, exactly, the pain was caused by...years later, when it started happening again, I saw different professionals who could not find anything wrong reproductively but who said it could be GI so I should go from there. Ya know what I discovered? I have a really stubborn gluteus medius muscle that kinks up on me and the pain refers to my RLQ!!! And I found this out without wasting time/money on MD visits. Thanks a lot, guys.
The huge lesson I learned is to never take no for an answer from docs and other medical practitioners. Your friend needs to be persistant, find out everything she can about BV and the related pain, and assertively take part in her own treatment. If her doc is not willing to pursue this more aggressively, she needs to tell him that either he work with her to get to the bottom of it, or she will find a doc who will.
Good luck to her.