The thing that is so interesting about addiction is that often......where a codependent mother leaves off......a codependent girlfriend or wife picks up. I'm so glad that you aren't continuing the unhealthy codependent behaviors of his mother. And possibly, because you aren't, she wants to play the blame game with you. He's using because you do/don't (fill in the blank).
There is no sense blaming anyone for your adult husband's addiction. Not you. Not her. My parents were responsible for raising me......but I am responsible for who I am today......just like you......just like your husband.
One of the tragedies of addiction is it often pits the rest of the family against each other.......while the addict sits back and watches the drama unfold. It takes the spotlight off of his/her addiction and they can use while the rest of family goes after each other blaming each other for the addicts antics or addiction. You have a choice not to be a part of the drama (as does everyone else but you're lightyears ahead of them because you can recognize the drama). I would urge you not to participate in the blame game.....that actually plays into an addict's mindset of "aha....see it's not me.....it was my parents fault!" That in turn causes the parent's to become defensive and do MORE codependent stuff to prove what great parent's they are/were.
We all get to be held accountable for our own stuff as adults. And it doesn't really do anyone any good to take another person's inventory for them. When I concentrate on taking care of my own inventory (and correcting my own defidiences of which there are many), I don't have time to point fingers at anybody else.
Just my thoughts.....
gentle hugs
ke