Hey tg... right there with you... my mother was sick/addicted too - the day of my greatest freedom AND the day I felt I was "myself" in the relationship was the day I choose guilt over duty.
I learned that it was sooo much easier to deal with guilt feelings for me than it was to have to "play" the perfect daughter. From that day on I had a relationship with her that I could manage and though she wasn't the mother I wanted - I gave that idea up and accepted what I had.
That took me to the end of her life and in the last year of her life - we had the relationship we both always wanted - too little to late - no - it was a miracle to me to have that time. I am now able to remember the good with the bad and feel grateful I got good at all.
I believe we all have different lessons and journeys to attend to. We also get to deal or not deal with it. I "chose" to do my part.
I am glad you came the decision you can live with - it makes all the difference.