Firstly i'm sorry for your loss.
Its a complicated and emotional situation.
I wouldnt think anyone from the family pities you, more wants to support you and help you all through it.
Could you perhaps meet up with your MIL and talk to her, I know that would be a painful and difficult thing to do but it may help. She probably thought she was doing the right thing to get people to rally round you.
I hope you manage to sort something out.
You are not a failure, not at all. So please dont think that.
Let yourself grieve and manage your feelings the way you need to.