I empathize with your concerns. I have not been those scary shoes with my S, but definitely with my teenager. It is a real fear!
Friends with bad influence can be damaging, no doubt about it. Unfortunately, you aren't the one to try and convince her of that fact about her friend. A wayward is much like a rebellious teenager. However, you can't ground her. All you can do is set clear, firm boundaries about what you will not tolerate......and stick with it. You can only control your actions.
If she is not already involved in an EA, it may be only a matter of time. It is a common pattern that falls within the behavior she is displaying.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!
