I WISH my MIL would detach like that! Trust me, it is so much better than having her baby him. My MIL is a control freak and that doesn't work well when you have an addict for a son. She is constantly in our business even when my AH is not using. She thinks she should be at his counseling appointments with my AH and she has called his therapist to give her advice on how to proceed with treatment for my AH!!! IT IS NUTS!!
But anyway, I know you feel a loss from your relationship with her but please realize it has NOTHING to do with you. She probably has just been dealing with his crazy addict chaos for so long she just needs to completely detach from it. I am sure she doesn't mean to hurt your feelings. My advice would be to just to back off for a while, she will contact you when she is ready. Until then, keep the focus on YOU, do something that YOU want to do just for YOU!!! YOU deserve it!
I pray that your ABF will grasp treatment and do the right thing.