Well, firstly. Don't go doing this girl's work for her. You may feel bad for her but it is her responsibility to take care of her, not you. You shouldn't feel bad for that. Secondly, you need to understand that you may not be able to help this girl and that's okay. Some people are beyond help and won't except help.'
I recommend giving her tough love. Explaining to her if she doesn't get her act together how can she expect her life to get better?
I presume she under age drinking, am I right?