Make sure if you're working with MIL that you keep it businesslike. You don't need/want to get her involved in this because its really not her business.
Many newbies try to get family/friends to sway their WW's opinions, but it NEVER works. Trust me, I played that game.
Again, She fired you, so she needs to figure out her own s**t just like you are figuring out yours.
Feel that pain. It [censored] but it is what will help you to realize that the W and R you had is dead, help you to detach and help you to move on/ move forward.
Don't show her that pain or anger. Use this board for that. I want you to know it's ok to be upset, and we all understand it. You are not alone.