I know it's hard when something like this gets sprung on you, but she shouldn't worry or feel that way about herself.
adamgunn's outlook on it is pretty much ours. Relative to other STIs it's common even though most don't even know they "have" it, it's not typically included in a STI screen so people who say "I've been tested and I'm clean" may or may not be when it comes to herpes, the whole HSV-1 and HSV-2 confusion, and so on.
I distinctly remember battling some herpes sores...I was like 9, and the more commonly used, and less scary, terminology there would be "cold sores" but really HSV-1. I don't feel the need to disclose that to anyone, even though if I was tested for it, I'm assuming it would be a positive. If I had a cold sore on my mouth, I wouldn't be playing with anyone, and if I had a sore on my genitals, I wouldn't be playing with anyone. Beyond that, I think that is really all you can ask of people since for the vast majority, the truth is they honestly don't know one way or another.
Other than doing some pre-play visual inspection to make sure no outbreak is going on, there's just really not a lot you can do. Condoms do offer some protection, but it's not complete. So, it's just one of those things where just about activity in life carries some risk, and you just have to decide for yourself where your risk tolerance line is at.
Starting to veer away from fact toward more opinion here, but I think the whole herpes thing is waaaaaay overblown, and just another example of sex-shaming by a culture that has a love-hate relationship with all things sexual, especially when there is money to be made off of it. A lot of things that we think are freak-out worthy, we have been taught we should be freaked out about, well beyond the level of what it really deserves. You may find this article interesting reading. How Herpes Became a Sexual Boogeyman
There are also several good older in-depth discussions on this topic here on the site. Threads discussing Herpes
Sending best wishes that this all will soon be just a bad memory.