I don't think you have to bail on her. What you can do is call your local AA and see what resources are available for people in her situation. You might also want to call your Mayor's office or the local police to see whate ride home services are available for people who drink too much. Most cities have something in place to keep drunks off the road. Have that number be listed in DrunkRideHome or MYRIDEHOME in her cell phone. Make sure to sit down with her over coffee and give her the information you have gathered and explain to her how what is going on and explain what you will and will not do. Sometimes people need a helping hand and bailing on her without letting her know in advance kind of sets her up for failure and you. Just get some information together and maybe even take her to an AA meeting, as a friend. Just help her get started on the path and make it really clear that you cannot be her drunk ride. Look up the term enabling and make sure she knows you don't want to be a part of her drinking. You can't be expected to do more than set her on the right path.