Cumcum74, I'm not an expert here but would like to share what I know. You may want to check out this STD website:

http://www.herpes-coldsores.com/std/

From your description, your gf's symptoms escpecially, sound very much like gonorrhea - yellowish discharge and burning sensation during urination like bro Pfizer has suspected. It's very easily curable but if it has developed into complicated stages, the damages to genitals are irreversible. It's better to seek medical consultation ASAP to determine if it's really STD. It could be non-STD but I wouldnt want to take chances. You might wonder why you don't have yellowish discharge yourself, like I mentioned on another thread, many carriers don't show symptoms. Hope you'll be fine. Cheers!