As the mother of a teen girl, I know that my daughter's friends are her community and her alternate family. In fact, this peer group is at the center of her personal solar system. As much as I might sometimes want to mingle with them or spend more time with my daughter, I try to remember to know my place.
Mothers of teens are on the outskirts of their kids' social group for a reason—you are not her friend, you are her mother. However, this is a group you need to keep an eye on, and this does not mean spying on everything they do. Stay watchful from a distance. If your daughter becomes a complete changeling by mimicking behaviors from her peer group that you know do not represent her real self, then step up to the plate and mention it. If you can do it with humor, you will disarm her enough for you to successfully get your message across. For example, when she sits down at the breakfast table wearing an outfit you realize blends with those of her peers but reminds you of a circus clown or, ahem, a lady of the evening, don't scream like a half-baked lunatic about her choice. Instead, say something like: "So, are you joining the circus, dear?" Or, "Wow! It never ceases to amaze me how so few clothes can make such a big statement!" Afterward, be prepared for her to sneer and growl like a Rottweiler tied to a junkyard fence. However, I guarantee that you will have conveyed the point that her attire is either laughable or too risqué while avoiding a morning screaming match.
How to communicate with your teen