I had a similar experience with one of my former step daughters. She was totally out of control, had a brush with the legal system after causing an accident while driving drunk without a license at 16. Her parents reaction was to take her to a counselor who said they had to be more supportive because she had poor self esteem which they took to mean little to no consequences for her behaviors. Eventually the court ordered her to AA and therapy. She never took it seriously, never did anything other than what she was required to do and to manipulate her parents into thinking she was an innocent victim. She is now 18, still drinking and acting in a self destructive manner. Her parents deny that she drinks, deny that anything is wrong because she had good grades and graduated high school. I fear for her future, especially since she is off to college in the fall, but only she can do something to change herself.
I know this isn't helpful in terms of showing a good way to handle your situation. But know you are not alone. I guess there comes a time when we have to accept our children are young adults and therefore responsible for their life choices, good and bad.