There are many situations in which adolescents have been given adult status. The general criterion is that the adolescent have an understanding of the situation. From what I've read about this case, this teen thinks the illness will do less damage to her body than the chemo. Truly, that is not an understanding of the situation. Chemo may not cure her, but the illness will, without it, kill her. If she were voicing an understanding of that, then I think most would be comfortable with her wishes.