Both the urinary tract and the genital tract meet at the external vulva in the dog. Licking here indications some type of discomfort. This could be from urinary tract infection, stones, vaginitis, skin infection, etc.
I recommend having her evaluated by your regular vet. I would start with a physical exam and sterile urine sample for urinalysis and bacterial culture. While these tests run (can take up to 3-4 days), I would start her on an antibiotic like amoxicillin also. Hopefully the lab results will confirm something as simple as a UTI, and that we are using an appropriate antibiotic. If the urine results are normal, I would move on to imaging of her abdomen using xray or ultrasound.
Good luck with your girl!
Please let me know if you have any further questions. If you are satisfied with my answer, please click on the green Accept button. Positive feedback is always appreciated. Thanks.