Well this is a case of you reap what you sow. She didn't just wake up an a self-absorbed, defiant, irresponsible adult. This is the child that you raised.
I think that family counseling would be a great step for you. You need to learn how to parent teens better, and she needs to manage her behavior, set some expectations for herself and live up to them. I think the two of you need a lot of growth, maturity and healing in your relationship.
She eventually needs to understand that living in a home (any home - yours or on her own) comes with responsibilities and rules. If she's not in school, she needs to have a job, pay you rent, pay some utilities, pay for own gas and insurance on her car, her own cell phone bill, groceries, etc. She needs to adhere to house rules on things like what time she comes home, whether or not she has guests over, foul language, drinking or smoking etc. and understand that even though she's technically an adult, living in her parents' home with younger siblings means that she still needs to be a good influence on her younger siblings and respect you (and your husband, assuming you're married). If she doesn't like that, she can move out and see what it's like to manage all of these things on her own.
I don't really understand how you got here. My two oldest are 15 and they know that after they graduate high school, they are expected to be enrolled in college or some kind of vocational school, join the military, or get a full-time job. I don't ask them to do chores, I tell them. And most times, they do their regular chores without being reminded and all that I end up telling them to do is additional projects such as pruning hedges or power washing the deck. Before they make plans for the day on weekends or on school vacation they ask "what do I need to do around the house today?" We're certainly not the best parents ever, but our kids understand that as a family, we are all responsible for getting things done. It's not an impossible concept to teach.