So sorry for what you are going through....it must indeed be hell. You are showing real love to her..just by being there.
I do have family that are very committed dubs and if it comes to it , I know that their decision would be the same as your Mother's.
Now, I am assuming that she is advanced in years and has practised the faith for a good long time (she is 'anointed, you say).. It is heartbreaking but I am sure that we must allow such ones the dignity of making their decision about their own bodies , even unto death. They may be misguided, misinformed , misled, but they choose to do it, so let them have their final wish.
My heartfelt sympathy,and admiration , be with you at this time..