How was your gf diagnosed?
Hsv1 can transmit to the genital area via oral sex, and about 50% of new genital herpes infections are genital hsv1.
Your girlfriend can take a type specific IgG antibody test to determine which, if any, type she has. The test misses about 30% of hsv1 infections, though, so if she tests negative for both types, it doesn't mean she doesn't have it. Was she originally diagnosed with a culture or a visual exam?
They should be able to do an antibody test to tell if the herpes she's been diagnosed with is hsv 1 or hsv 2. Hsv 1 (oral herpes) can transfer genitally but not the most common thing. About 80 percent of the population has hsv 1(mouth herpes).