You might want to use Derma-IonX orally. Derma-IonX which is an oral homeopathic product stimulates the enzyme systems in the body which reduces inflammation, promotes healing of the skin and helps with assimilation of nutritional components in diet and supplements. The supplements I use along with it include Canine probiotics, vitamin C, MSM, and Omega 3,6,9. Together with Derma-IonX it produces a synergistic effect for a faster response. I would also suggest that you give your dog only filtered water for drinking and bathing if your water contains chlorine or fluoride. For the dietary modifications you might want to try a grain free diet for a while. You can spray the outside of the genitalia avoiding the mucous membrane. However spraying it may encourage her to lick it off and continue the licking cycle. The other thing I think you should do is to go out with her when she has to urinate and the press up on the bladder near the end of urination to express the remaining urine in the bladder.
Please feel free to contact us again if you have any other questions.