Mom has stage 4 lung cancer that took on the brain

I am overwhelmed with sadness. Her diagnosos came only 2 months ago. Lung cancer that had also moved to her brain. They radiated her brain and the maintenance medication has made a vegetable of her. She is 77. Overcome many a health issue before but it seems she just isn't going to take the next 6 months of chemo standing up. I really didn't think she would just not get up and fight this. She does talk of plans for next year, a grandson's wedding is planned, but at this rate I don't see it happening. As one of many daughters, we dicuss all the options, how to handle Dad who feels so helpless in all this, what is and should be done but Mom just isn't on board. I can see all the physical, financial and emotional weight building on us all already and I don't see how we will get Mom on the team. We are fortunate to have such a large group of care givers even though we a re spread across the states. It will be my week to be in attendance shortly and I know my frustration wil be right there out on my sleeve. How does one deal with all this? I would hope the efforts to keep her quility of life up to some standard would be the goal but at the moment it feels like all is lost.

Other than the negative vibe among us all at the moment, the cancer itself has not progressed. The lessions in her braing have been "radiated" and will be a couple of months till the reassessment.

How do i lift this dark cloud of sadness? I won't be much of the caregiver/mother/employee/sister/daughter with that hanging around.