There are so many kinds of brain tumors. My father died 4 1/2 months after a diagnosis of a stage IV Glioblastoma. He was 74 and chose not to do any of the invasive treatments. I treasure every moment I had with him.
One of my mom’s friends is a 10 year survivor of a brain stem cancer. She gets along remarkably well much as your friend does.
What this young woman has chosen is very selfish. She has a lot better odds at her age in prolonging her life than my father ever had. It makes me very sad for her and her family.
What would be really sad is that doctors make mistakes, and what if she isn’t really terminal. A lot of people who were told they had less than a year to live were still here 10 years later.