I'm sorry for the pain you are in.
I'm sorry you won't be able to spend more time with your Mom.
I'm sorry for all the memories that you could have had together.
Make the most of the short time you have together. Let her know how much your relationship means to you. Let her know how much you will miss her when she is gone. Let her know all the love you have not been able to give her all these years.
Soon she will be leaving and I'm sure she doesn't want to leave you. But the disease has taken its toll. For her the peace of death is favorable to the pain of living.
She is not leaving you because she wants to go. She is not leaving to hurt you. Soon she will free of all the pain. Soon she will be singing with the angels.
It doesn't bring you comfort to know this. I wish I were able to take away your anger and pain.
I'm sorry