Something else you can try that I've found extremely beneficial for all my dogs, and does no harm.
Fold a paper towel, and wet it along the fold with apple cidar vinegar. Rub it vigorously but briefly on first the vulva and then the anus (be sure to get the order right, because you do not want to spread bacteria from the anus to the vulva area).
Do this once a day. If she resists it at first, give treats. Soon she will realize it doesn't hurt at all, and she will relax about it. Once a day is enough, but do it every day.
This seems to help with bacterial infections and also with anal glands. And it does no harm.
Also, it would be a good idea to have the dog's thyroid blood levels checked. Hypothyroidism can cause problems like this--and many other propblems, too.
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Kathy Diamond Davis, author, "Therapy Dogs: Training Your Dog to Reach Others," 2nd edition, and the free Canine Behavior Series articles at http://www.veterinarypartner.com/Content.plx?P=SRC&S=1&SourceID=47