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Get the STD screening tests repeated. Her symptoms suggest possibility of infection. Vaginal pH changes once the girl starts having intercourse, making her more susceptible to infections. She will also need a vaginal smear test to be done to look for and identify infection. Another possibility would have been vaginal dryness causing the pain, but this would be resolved with using lubricants.
Do not let her ignore her symptoms. She should focus on getting to the root cause of the problems. Once the cause is identified as infection, you too should get treated simultaneously for it and avoid having unprotected intercourse while being on treatment to prevent chances of re-infection. Ask her to visit her gynecologist soon.
Take care.