Me and a mother

What to say to a mother who has recently started to deal with a chronic disease that threatens the life of an adolescent daughter? What to say if she is suspended between a possible terrible verdict and the hope that reappears, but is almost seen as a threat to paradox. If things go well, as it seems, it would be even more unbearable to be disillusioned later. 
Do I defend myself behind the white coat, which incidentally I do not wear, and do I treat her as a clinical case?  Do I frame her in an elegant diagnosis and give her something to relieve the intolerable anxiety that doesn't give her peace? 

But what to say, that has not already been said, and that doesn't sound affected or unnecessarily comforting, or misplaced. 
The words come later, I sense. Now,  I have to live her same anguish, and stay there, present, while the images of my children continue to turn around into my head. 
I have to let the pain bounce between me and her, and then try to face it together: with a presence at your side pain is just a little more bearable. I hope.