Clymidia Time Frame

about a month or so now my girlfriend showed signs of an PID (pelvic inflammatory). We went to the doctor and she diagnosed it as such. This lead to a test for an STD. Chlamydia showed up with a positive result. This was after being together for 10 months or so. My question being, i may or may not have had it before we started dating, i am not sure. I am curious though if there is the ability for it to remain dormant for an amount of months maybe showing very little signs if any at all, then showing up with a green discharge (that we both discarded at UTI) then disappearing again and showing up as PID. She is insistent on my infidelity, i know this is untrue. Is it her infidelity or is this case possible.  

[Vance2335]

Dormant is not the right word, you don't have to have symptoms as most women don't and about 1/2 men don't. Most of the time PID takes longer then 10 months to develop, so this might have been preexisting to her.