About 6 years ago when my brother in law was living with us for a short time, I remember him coming to me with the same exact problem that you are describing. He was dating this really nice lady but he was having a really hard time being up close and personal with her because of her pungent smell coming from the vagina area. And it wasn't because she wasn't "clean".
What finally worked for him......was when I finally handed him a bottle of vinegar douche. I have no idea what he told the woman about why he would have something like that, but he said it worked. Maybe try putting some vinegar in her bath water. I think it has something to do with the p.h. balance that a woman has in her vagina. Vinegar is a natural douche. It is cheap and I think it would be worth a try. The vinegar douches are the only ones I would ever purchase.
Also this woman my brother in law was dating was a big beer drinker. The yeast from the beer may have been what caused the strong odor. Who knows.
That is the only experience I have ever had with this subject.
I know that you always hear that douching is bad, but I have done it a few times in my life (the vinegar ones) and I haven't ever had a problem.