Well.....this sounds like quite a hell of an existence for all of you. And I'm so sorry for the anguish you are all experiencing. Particularly those children......
When someone has dug a deep hole, it really doesn't do them any good to crawl down into that hole to throw them on our backs to carry them out. It simply doesn't work. And often.....it destroys both people.
Fear is kept me (more than any other member of my family) tied in to the chaos. I understand your fear......but the moment I let go of it, was the moment I found peace in my life (my son is an addict who is struggling with sobriety). I understand the cycles of desperation.....but I had to step off the rollercoaster to gain footing in my own life. I did it with the help of Nar-Anon and private counseling. It worked for me.
There are some very positive things in your post.....hard to spot.....but they are there. Her children are safe. That's the biggest positive.
Sometimes.....right before things begin to change.....they get really really bad (at least this has been my experience). Hopefully, she is on the verge of change.
You and your dear family will be in my prayers.
gentle hugs
ke