Welcome, and big hugs to you. My son did something similar when he was 17, and we have not seen him in years. It's very hard to say, but it does get easier as time goes by. I honestly don't know any longer how I would feel if he showed up at our door. I think about him often, though. Usually with regret that he isn't happier. I can't regret what my role was in his getting to where he was, because there really is not anything I "did" or "didn't" do. I was just a mom, doing what mom's do. Perfect? Heck no! But was I as he sees me? Absolutely heck no!
As a point of observation, I would offer that not only has God not done this to you, whatever "it" is, it hasn't got much to do with you at all. This time, it's all about her. She is doing this to herself. We are just observers in our adult children's lives. To be sure, some people get to observe their happy well adjusted adult children, and even get asked for advice. These parents always need to bear in mind that the advice may not be acted upon :wink: I'm sure it's much easier to observe our happy kids than it is to observe the out of control ones. But as adults, we really can't make their life choices for them. They get to do that all by themselves, and all we can do is stand back and watch and hope that no one gets hurt. Like watching them learn to ride a bike or drive a car.
My other thought is, her sudden druggie like behavior may be a change, but can you be absolutely certain it's fake? Do you UA's that are clean? If she has been running away two or three times a year, drug or alcohol abuse doesn't seem like a great leap. And there are very popular highly addictive drugs that can make a mess of a person in a matter of days.
I know that thought isn't much comfort, and I hope that you are right that she is faking. But honestly, in all of the years I have been reading people's stories, "faking drug use" is not one I've ever heard before. I've heard "it's not that bad" (unfortunately it usually is that bad), and denials that it is an issue in any way shape or form, but it sounds as though you might want to talk to some people who know more about her situation to help you understand what is going on. Unfortunately, I think we don't ever get to know "why". In the long run, "why" doesn't matter much, anyway.
Good luck to you.