Hello, and welcome to HCM!
The symptoms you are describing in your girlfriend are most likely caused by a urinary tract infection
or a sexually transmitted disease
such as gonorrhea
or chlamydia. There are other, less common causes of these symptoms as well. She would be wise to see her family doctor or gynecologist soon.
As far as what you should do, it depends on what diagnosis she receives. Of course, if she is diagnosed with a sexually transmitted disease, you would be at risk for the same infection. In this case you should be examined by a physician and tested as well.
Wishing you good health, thanks for your question!