My husband was diagnosed with glioblastoma a year ago and everyone rallied around. Then he had radiation, chemo and Avastin and he got better. Though watch out for the last 2 weeks of radiation and the few months after the patient can be awfully tired. He never had nausea. The tumor was always in his brain it had just stopped growing because of the treatment.
My husband seemed fine this winter. He even went skiing 6 times with an instructor. Unbelievable! He has flown across the country to visit people and go to weddings and events. I don't know how many people have said to me "He has it licked." "He's not going to die." Most people did not see the changes in his personality that I saw. They couldn't believe that this was a burden at all to care for him. Now he has had a recurrence.
The first symptom of the recurrence was a grand mal seizure at the gym while he was on a treadmill doing his regular 3 mile walk. He is now on a trial drug and probably headed to hospice in a couple of weeks.
There is a culture in this country that death can be prevented "if only" you ate right, exercised right, prayed right, lived right, found the right treatment, etc. Many people in the US do not see dying as a natural part of living. But we are all dying from the day we are born. Watching some one die is horrible but it is part of life and it is an opportunity to form bonds that cement that relationship forever. You also will never regret the time you have spent with your loved one.
My only suggestions are get as much help as you can afford or is available through hospice your friends and relatives and your church or community. Everyone is willing to visit but get help with those chores you hate. Cleaning, yard work, shopping, car washing, etc. Sometimes having someone sit so you can get out even to do the grocery shopping can be important.
I am glad (at least today) that I have had this year with my husband and I do not regret the decisions we have made. I figure those who have not been here can't handle it and that's ok. It's their loss and if they will do something for me that they are comfortable with then that's great. If they can't do anything then that's ok too. It's their problem not mine.
This was a longer message than I intended. Take care. Love your sister and do what you can for her. She will need you. Don't think about anyone else.
JMB