Hello there, I have been dealing with staph in my groin area for over 2 years. A total of 5 infections so far. I came across a research where they recommend a dose of the probiotic called bacillus subtillis. I purchased it from amazon of United States since it wasn't available in Canada. I am hoping the infection stays down. you should give it a try as well to stop staph. Google, bacillus subtillis for staph and read up on it.
Since you are having staph infection, so if your girlfriend has been diagnosed with staph infection then chances are there that the infection got transmitted during physical contact like sexual contact or skin to skin contact. It is very surprising that the infection has not shown much results with antibiotics, In such cases, it is advisable to get the culture sample from the sores and a biopsy skin done which will confirm the diagnosis.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.