There's been a lot of good stuff said on here already, so I'm just going to add, because it's been referenced a couple of times:
Herpes can be transmitted just through kissing, even if there's not a current outbreak. So while there are other, perfectly valid reasons for asking for safer sex practices during oral, cold sores/herpes isn't one of them. She could kiss someone, get it, and still transfer it to you even by following all the safer sex rules during oral with other people.
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack