How do you know if she likes you are not?

I have been hanging out with this girl I met at my old job. We have been hanging out for awhile now. First date was nice, and we kissed intimately. Second second date was not so touchy but we hugged and kissed. Third date, I had to leave on emergency, she didn't want me to leave. She kissed me goodnight. Everything is good but sometimes she would flake out on me. If I was supposed to pick her up at a certain time, I came over and she was soo tired from being drunk the night before. There are also times where she would not even pick up. But when we do hang out, we have a great time together. She's comfortable with no make up in front of me, she even let me in her bed room. She would drink off of my wine glass. She would kiss me. I don't know what it is. Mixed signals like crazy. Sometimes she would answer and sometimes she would not. How to deal with this and how would you know if she likes you or not. What game is she playing? What should I be doing to get her to move on to next step with me. Please help.