
This often happens with bitches that were spayed before maturity. It is called sometimes Infantile Vulva. the Vulva has never developed along with the rest of the bitch and becomes sunken and can cause infection and urine scalding in the groin, the liciking then makes matters worse.
the only thing I can suggest is that you wash her with a baby bath liquid or diluted Hibiscrub(an antifungal antibacterial wash used by vets and doctors to scrub up before operations and for cleaning skin) and apply vaseline to protect the area from the urine burn and the licking (as you would a baby in nappies).
If there is definate redness and signs of infection then a trip to the Vets and a course of antibiotics may be needed.
This is another reason I advise against prepubescent spaying, as I ahve seen this problem among several bitches of people I know.