This is a delicate situation as the way it is presented could very possibly lead to future secrecy from your daughter about who her friends are. In my opinion, the best way to approach this situation is to begin asking your daughter some very basic questions about this friendship. What does she like about her friend? Why does she like spending time with her? Does she think she makes smart decisions? Etc, etc. Perhaps such questioning will lead your daughter to draw her own conclusion about her girlfriend's values. Maybe she'll have the opportunity to see her friend in the same light that you see her. Allowing her to draw her own conclusion with the values that you have instilled, will help to avoid resentment of the feelings you have formed about a friend she has chosen. If her friends' values are truly "distorted" and repel her own, some strategic questioning should help to clarify. However, keep in mind the possibility that regardless of our rearing, it is possible and sometimes inevitable that our children form their own unique values. I hope this helps.