I have much experience in the are of and I'm not afraid to say the word vaginitis or vaginal yeast infection. I've had constant infection for going on 8 years. I understand where you're coming from with knowing that you won't totally eradicate the local infection until the systemic infection is treated, but what can you do now to limit the discomfort locally.
Well, for me I'll tell you that as far as diet, as of this time, I'm not on the diet as of yet, but plan to. But I have weaned myself off most REFINED sugars like cookies, cakes, sugary cereals and all that other garbage I used to crave. Believe me, it is a weaning process and its best to go slowly or you may regress. Actually some peole can get withdrawl symptoms similar to stopping coffee and cigarettes. I think I'm doing much better that way because my body no longer craves the garbage. We (more like me because my husband could barely get any) used to go through 1-2 half gallons of ice cream a week. All those sales at the market for cheap ice cream were irresistable. Now when I see the circular with the big picture of some Breyers it doesn't even tickle my fancy anymore. Again I'm getting off topic.
Anyway, I noticed that the vaginal yeast has gotten to be more of an annoyance than a major disruption due to the reduction in refined sugars. I'm just working on the natural now. I remember years ago, it used to be so bad that I was hurting trying to walk down the street. And its hard to tell my (at that time) new husband about the vaginal pain was the reason I couldn't walk too fast. Also I used to scratch like crazy in the shower because the warm water increases the itch much like a mosquito bite. But that's all ancient history now.
I might get an occasional flare up now and then and I've learned that using some virgin coconut oil on some toilet paper and applied to the affected area is a wonderful treatment and works within hours for immediate relief. Just make sure you use a pad. You don't have to apply at night. I usually only need to do this one time and that's sufficient for myself.
Hope this helps.