Maybe now would be a good time to try and reach out to MIL again. It sounds like she could use a friend right now. If she turns you down --- just try to remember that she is going thru alot right now. A card with good thoughts might be a nice way to start some communication. Good Luck!
I have a friend going through this very thing. She has been doing a lot of reflecting on her life (workaholic) and this may be what triggers her to change that.