Look, maybe my views are a little skewed because I don't have an STD myself, nor have I ever been with anyone that has had an STD(or so I'd like to think), but if that girl knew that she had an extremely contagious disease like herpes beforehand, and still neglected to tell your "friend", then you should tell your "friend" to dump that slut.
I mean Jesus, I'm not even involved in this situation and it's freaking me out because who knows how much of this is out there? There are already enough people out there that have STDs and don't know about them that are still having sex, and the fact that there are people that know they have something so obviously detectable like herpes and don't say anything is kind of frightening.
I've never had sex without a condom, and don't fucking plan to anytime soon.