Hello LD.
So sorry to read of your treatment from mom and your sadness. I am getting some of the same from a few in my family. I came to realize that these people were in the control of the cult and or close family and unable to reason and think or even feel the normal ties for family.
I don't know if this helps any, but I have resolved that I have the right and responsibility to myself to find and enjoy happiness. I will be goddamned if I will allow a few unfeeling relatives spoil that.
To deal with this I made a mental decision that as long as they behave this way, I will have nothing to do with them. This gives back to me the control of my own life. If they indicate that they want to talk to me, I tell them that they must drop the shunning or forget it. I had three siblings I have not heard from in 11 yrs. Two have died recently and since I told them this 10 yrs ago it is like they died at that time. I had my grief and tears then and when they passed away it was not that upsetting.
In the last 10 yrs I have found a measure of peace and happiness. I am contented with life and with myself. I believe this was made possible by removing any source of criticism or control by guilt or emotional blackmail from my life.
I also had to accept that I can not make-cause-wish-manipulate or threaten any one to change their views of me or accept me as I am. That is wholey up to them.
I know that some will label this as a cold and unchristian way to behave. So this may not be what others find acceptable. I lived in the field of grief you described for about two years before I began to look to myself as the only source of protection for myself. If I personally did not set up a set of rules regarding how I would let people treat me I could expect more of the same.
Each person has the right and responsibility to respect themselves and not accept the unacceptable treatment of others. What good are we to ourselves or our loved ones and others if we do not nurture and protect ourselves?
Hope you and your family find some measure of peace and happiness. It is out there.
Outoftheorg