Hi NikNox,
I actually never dated an addict or anyone I thought drank too much prior to meeting my husband. When I met my husband he had been clean nearly two years. My experience with recovery was my dad went to rehab for 30 days and did not drink again for about 25 years. my dad then started again but stopped and I have not asked why. I feel he knew he could not control it still and stopped on his own. So what I knew was that addicts recover, which they do but they also relapse. I will say I fell right back into that co-dependant role with my husband though. I never saw it coming the small changes in me along the way in response to things he was saying and his behavior. I have only been dealing with knowing about his relapse for 4 months, but sensed something was going on for a while and was right. My husbands attitude and behavior towards me has been strange for over a year. He told me he started using again in May, but I don't believe him. I pretty much don't believe anything that comes out of his mouth even though he is on suboxone now.
I can also say that to this day I have to go through a period of guilt when I buy something for myself. The book I am reading has quotes from people stating the same thing. How they never feel they can ask for anything or want anything. I thankfully talk my way through and get what I want. I am learning more about myself everyday. Not sure what kind of participation you can get from a teenager to read up on this, but maybe if you word it the right way?? She will not want to hear that her mom is bad in anyway at all. If you even say we know you have a lot of responsibility because of your moms drinking that will be what she hears "moms bad". It will most likely turn her off instantly.
Her mom has a medical condition also you stated and children become co-dependant for that reason also. If you can approach it in that way she may want to do some reading on it or see someone and talk. A medical condition is not her mom's fault, so it may be a way to start.
I would suggest a child counselor, but also realize that they are not that popular there as I have been told by my husband and his family. If you can find a good one they may have some other approaches for you to use. If she was to read on co-dependancy I think she would see herself in the words. Just understanding the situation and yourself in it helps a lot with stress and anxiety.
Again prayers for you and yours