Cancer is a rough road. My mom is now 9yrs into remission, but I remember the anger and denial I faced initially, and am sorry you have to see theose same dark places.
Keep in mind that after a trial like this, the eventual end, as horrible as it sounds, will bring peace to the person's life.
Medicine has done what it can, so now its your turn. Hug her. Spend time with her. Succeed. These are things that will make her happy. Your family fighting? It can only make her position even more difficult, and you all need to see that.