I used to be pre-med and it sounds like it could be a more serious problem, has she been tested for HIV? HIV makes it hard for the body to fight off infection. One of the earliest signs is constant yeast infections and the bacterial infections are similar because the yeast infection if not treated could go bacterial. I would most definitely have her checked, go on the internet and search for places that do it for free. There are places all over the USA that do it for free, one simple cheek test or sometimes a blood-test depending. As far as lowering her risk, first I would like to say that condoms say that are up to 90 some percent accurate. When tested the best ones come out to be only 65% accurate. I'm not sure where to get it, but on top of a condom apparently what works good (never been sexually active, just heard about it from word of mouth) is a contraceptive gel that goes in the vagina. Although this gel will claim that you don't need a condom when you use it, I would use both to be on the safe side, which might decrease her risk.