I used to do meth and alcohol. I quit meth long before I ever had a child. 2 years is a pretty good long time to be clean IMO.
I agree that it sounds like the x-husband maybe holding on to some resentment. I hope you will keep fighting for this person. It sounds like she has done a lot to restore herself.
I think she needs encouragement to keep trying and showing up cause her kid will see that she does keep showing up and that she does care and I think that is very important.