Awwww, I am so sorry that another family has to go through this but as everyone has told you...you found the right place to help you grasp things that are happening or if nothing else...a great bunch of people to talk to who will listen and not judge your parenting skills.
The addict in my life is also my daughter and unfortunately I have no control over that. She has been living from house to house since she was 16 years old when I had had enough and sent her to live with her father. He found out quickly what I was going through and put her out as well. Life has been going downhill for her ever since. I found out the hard way that letting her back into my home was not the answer and the life that she is leading is by HER choice..not mine. She had two wonderful children that she gave up in the meantime that I am raising because she again..Choose this lifestyle. She has never wanted help as far as rehab until a few months ago. I gave her a choice to only call me when she was ready to get clean. I got the phone call drove her hours to a DETOX center only to have her check herself out.
Letting your daughter back into your home isn't the answer. Why put yourself through more hell caused by your addict? I know you love your daughter...as I love mine but we can no longer be held responsible for their fate. I wish you the best of luck and please stick around..there will be numerous post from others that may help you understand more!