How many chances should one person get?

I work with a girl who shall remain nameless. She has alot of personal problems. Bad relationship, drug abuse etc. The whole lovely package. She keeps calling out. Last night we were finally busy. The owner had to pick up tables.. She called out 15 minutes before her scheduled time. I was supposed to get off at 6pm, wound up staying til 9pm. More money for me, which is great, after the last two crappy weeks. The point however, is she has been re-hired 3 times. I think it is time for her to go. Her personal life is at the point where I don't think she is able to hold down a job. How would you like to know that while you are waiting for your meal to arrive that your server will be right with you because she is currently in the employee restroom smoking crack or shooting up? I will not let her in my cash drawer. I like her as a person. As a co-worker I do not. They are getting ready to clean house and I am wondering if she will be part of the clean-up. My boss/owner is a very fair man. He told me that he never fires people, they fire themselves. Plus, many of us are in recovery there, and it is many of us don't want to work with people who are still using. It's blatant. I would hate to see anyone lose their job in this economy. I have pulled her aside privately and spoke to her. As a friend who has been there and done that. I have hugged her and watched her cry. I am tired. The extra money was nice, but I made a bet with my boss..A $5 bet. He gave out w-2's Thursday night. I bet him that many people would call out in the next 5 days. He said no way, not on his shift at least. We shook hands and than the phone rang.. L$#$% called out. He owes me $5!!.. Have a great day...