I am assuming you are in the USA.
Quote:Doctor-Patient Privilege
Once a bona-fide doctor-patient relationship is established, the duty of confidentiality"attaches," and in many states, the doctor can invoke a legal privilege, on the patient's behalf, when asked to disclose or divulge information the doctor may have or know about the patient.
http://www.enotes.com/everyday-law-encyclopedia/doctor-patient-confidentiality
If the doctor or any of his staff were to tell ANYONE it would cost him his career. He CANNOT disclose the nature of a consultation for any reason to any person. As I understand it A doctor or his staff cannot be forced to testisfy in court about information under doctor - patient privilege.
It is impossible to tell if a woman has had intercourse from a physical exam.
The hymen which is what most people are concerned about can be broken by activities such as riding a bicycle, horseriding, gymnastics, or any of many physical activities.
Evidence of sexual activity can only be determined by sampling for sperm traces. This would not be necessary in her case. Even if swabs were taken to test for a urinary tract infection no tests for sperm would be ordered.
However your girlfriend should disclose sexual activity to her doctor. He needs to know all the facts to make an accurate diagnosis.
She should also disclose the fact that she is very concerned that someone may tell her parents that she had been to see the doctor and request that staff be particular about privacy.
If you GF feels the need she can tell anyone who needs to know such as nursing or reception staff she has an earache and wants to have her ears examined. In most cases reception and nursing staff will not need to know of her reason for visiting the doctor.