J., God Bless you. it sounds like a terrible situation to be in. Everyone who answered before right. But here's a simple breakdown for your problem, and for any other you might encounter. If you are uncomfortable or unhappy with someone or some situation, then stop engaging with it. There is no miracle that will happen because you acted in a certain way with someone who is abusive and addicted to drugs. You will not change her behavior. But you can change yours. What are you really getting out of the relationship and is that good for your life? No matter what the details of a story are you can ask these basic questions; How do I feel when I act this way? and, What can I do to make sure I feel good about my actions?
No one is forcing you to do any of the things you are doing. Sure your mom trained you, but like you said you are an adult now and even the most subversive forms of familial hypnosis must be addressed by the adult child. And that starts with choosing not to be in situations that dont feel good to you. Stop blaming your mom, take better care of yourself and feel better about your own choices starting now.
Good luck, old habits die hard. If one of your family patterns is drama and victimizing or being a victim it can be hard to be disloyal by stopping your involvement. But no one else in this situation is going to change it, and you can only change it by getting out of it.