You have to decide what your boundaries are. You can't stop her from drinking, but you don't need to be complicit in her behavior. So I would say, no, you don't go to a bar with her. You also don't bring alcohol into the house. I understand about wanting to keep her safe, but I can tell you from experience that doesn't work. You didn't cause it, can't cure it, and can't CONTROL it.
This is hard for all of us in the beginning. We all make the same mistakes when dealing with someone we love. So no one is judging you here, please believe that. That's why AlAnon is so great....lots of experience and non-judgemental support.