Sorry to hear of this pain. Please let me know how she behaved after your husbands passing.
and if you ever shared your feelings with her about the experience.
She acted in an inappropriate manner and not just because your husband had just passed but also out of respect that you are her mother in law and mother of her husband. You have tired to be kind and cordial but it sounds like you may need to speak with her directly and set the boundary about what you will tolerate from her and how hurt you have been. I would also talk with your son and let him know how you love and care for him and want an easy and harmonious relationship with all.
*please don't give personal info here such as your phone number. Once we are done, I will write to customer service to have it locked for privacy reasons.
I am here when you are ready.