Herpes Doctor

I've been making out with this girl lately (I am a male,) and every time we do it, a few days later, she gets a cold sore on her lip, but I get nothing. She's made out with other people before and it has not happened to her, but this is my first time. I had a cold sore once many many years ago on my lips, but I've never had one before or after that, and am not getting them now, it's her that gets them.

I thought that if I do have HSV-1, I should also get at least some symptom. I don't know if I have genital herpes (I've never had oral sex or intercourse) but I don't see how or where I could have gotten it, my parents do not have it.