If i already have hsv-1 orally and i have sex with my girlfriend who has hsv-1 on her genitals, can i be reinfected on my genitals?

HSV-1 or 2 does not have a preference for location. Once you have the virus, it may recur as a rash again in the future. Please review: https://www.cdc.gov/std/herpes/facts-brochures.htm

Presumably you have HSV-1 antibodies and it is very unlikely that you could reinfect another area, especially since HSV-1 tends to prefer oral to genital mucosa. However, if either of you is having an active outbreak it is just common sense to avoid contact in those areas.