Cold sores are ALWAYS caused by herpes, usually the virus hsv-1.
8 out of 10 people have hsv-1 on their lips, in fact, there is a good chance you have it yourself - especially if you have ever had a cold sore. Most don't know they are infected.
Unfortunately for your girlfriend, some people never get outbreaks and others get them a lot. She obviously gets them a lot.
If you are not infected with hsv-1 on your mouth yourself, you could either catch cold sores from kissing her or get genital herpes through her giving you oral sex.
Although she is most infectious when she has symptoms, she can also sometimes pass the virus in between - my boyfriend, like her, gets regular cold sores, and he gave me genital herpes from giving me oral sex despite the fact that he did not have a cold sore at the time. It is known as 'asymptomatic shedding' of the virus.
You don't have to stay away, just be aware of the risk, and be prepared to take it. I was, and I still think it was worth it. Obviously avoid kissing or her giving you oral sex when she has a cold sore. Also avoid it when she has a cold or is feeling very run down - her immune system is low then and the virus is more likely to be active. Don't have lip contact with her during or for a few days after a cold sore.
It might help if you went for a blood test for herpes - they can see which, if any of the two herpes viruses you have. It is likely that she has hsv-1. If you also tested positive for hsv-1, then your risk would be much reduced. In that case, avoiding contact when she has an active sore would be enough of a precaution.
If you didn't have it, you might want to take the precaution of using condoms if she gives you oral sex. But you would need to remember her mouth could only make contact with those parts of your genitals covered by the condom - anything not covered and you would still be at risk.
I am glad you feel that way about her. There is no point in being judgemental, most people catch cold sores from close family when they are small children, and they cannot help it.
I guess I thought I would never catch it, that it was only I risk when he actually had a cold sore, but I still caught it. Saying that, it took me nearly seven years, since someone with cold sores is obviously not infectious all the time.
If your girlfriend is aware of her own body it helps. People can often feel the virus activating - it is known as prodrome. It can be a tingle or itch on the lips, or sore facial skin or nerves on one side. She should avoid lip contact with you when she has these symptoms too.
My sister caught genital herpes four months into her relationship with someone with cold sores. I still think the reason I didn't catch it for so long was because my boyfriend was so careful about noticing his own symptoms and avoiding coming near me if he thought there was a risk.
If she gets cold sores a lot, she might want to look into suppressive therapy such as valtrex or acyclovir, or at least take them when she feels a cold sore starting. They can be expensive, but a lot of people find they are worth it.
I have genital herpes hsv-1