If she's genuinely doing it for herself, that is a VERY good sign.
It doesn't mean she won't relapse, but it does mean that she wants to get better for herself, not just because you told her to - and that she's actually willing to work a program, rather than just go for the motions.
My XABF never got that far.
I am so happy for you!
As for the MIL, I agree, she should see her daughter now. The truth can hurt, but the truth can also heal, and right now the more supportive people in her life that are exposed to the truth and educating themselves about her problem, the better your wife's chances of recovery will get because she'll have fewer places to hide from her own consequences.
I never truly understood the meaning of "tough love" until I became involved with an alcoholic.