I believe my ex loved me the best way he knew how.
That does not mean that his behavior was okay.
From what you are saying she did choose to walk away. She also choose to not treat your kids appropriately, and she chooses to continue to use her DOC.
I am not saying she is in her best thinking when she does those things....but they are just as much a part of her as the loving, kind and wonderful person that is there too.
It did not change in my relationship until I changed....then it stopped mattering what the A did. I was on the road to recovery.