What would YOU do in this situation?

i have a female platonic friend, that has a friend that contracted . herpe chick continues to sleep around with whoever will have her, often neglecting to tell her partner that she has . it scares me to think of her screwing some dude who then sleeps with a different chick who then sleeps with me. so i tell my friend that she should scold her friend for her irresponsible behavior and/or stop being friends with her. but my friend is very non-confrontational and won't say anything to her. i have considered outing the chick to everybody i know, just to lessen the chance of some guy getting from her without knowing, but i'm fairly sure that it's not my place to do so. so what would you do?