Serious vent coming on.

I have a friend, she is 18 and just found out she has herpes. She's only had sex with one guy (her boyfriend) and says she has always used a condom. He had a cold sore and apparently "kissed" her down there. Well needless to say she broke out in sores and I encouraged her to go to the doctors. She did and finally after a lot of pushing she called to get her results and she tested positive for HSV1. But now she's refusing to tell her boyfriend because she said if she has it she got it from him and she doesn't see them breaking up anytime soon so why does it matter. I told her it matters because either he doesn't know he has it or he knows and didn't tell her either way he deserves to be told so that he doesn't spread it around at any point. Also I said if it were me I'd want a full std check for both myself and him and she was like why I asked wouldn't you want to know. She says not really. Is it just the age? I mean she's 18 and I'm 25...but seriously this is so irresponsible and not ok!!!!