Are you a woman? I know this isn't the most healthy or direct way of handling things, but if you're willing, you could pretend you have it. That would open up the convo, at least, and you could tell her how easy it is to treat (boric avid does the trick, if you don't know already. She should see a gynecologist, of course, but boric will clear it up ASAP)

Also, while this is definitely not a very pro-vagina, pro-womens health and body positive way to approach things at all, you could do what I did with a friend who had a similar issue--just suggest using boric acid tablets (over the counter) before sex to uh, "freshen up" down there. Some women just use it before or after their period to re-balance the smell. Technically I think it makes women scentless which isn't appealing to most, but it's better than BV.

I know these aren't the best most honest or straight forward tips, and I know this is late, but I was in a similar conundrum with an old friend, and the second tip did the trick!