Are you negative by testing, or basing that on symptoms? I ask because 90% of those who have oral hsv1 never get symptoms, and the hsv1 IgG blood test misses 30% of infections.
That said, if you don't have it, you can definitely get it from her when she doesn't have symptoms. We don't have transmission stats, as it hasn't been studied like hsv2 has.
We know that 67% of people under 50 have hsv1 globally. The closer you are to 50, the higher the chance. I'm not suggesting that you try to get it, or don't take chances to not get it, but you are denying yourself kisses from your girlfriend. That's probably not sustainable. You deserve to have intimacy, and she deserves someone who can relax enough to be able to at least kiss her.
Are you just now realizing she has this because she got a cold sore? Is that why suddenly you are feeling stressed about this?