Such a touching story, thanks for sharing.
As sad as it is, one can't help feel for one's patient. Its so difficult sometimes to notice someone who was so 'up' and so full of life and then see them later on, and deteriorating down hill. Almost, like giving up their will to live because one doesn't want to do it anymore. My only experience with this was with my dad's dad who was in a nursing home for 5+ years, and slowly deteriorated over a period of years and eventually died there. Each time I'd visit him he'd be different in some way or another. It can be heartbreaking, we're only human after all.
I am not a nurse, yet. And, I have alot to learn. But, I can imagine there is only so much one can do for a patient and the rest is up to him/her and God. After all the meds, tests, labs, therapy, interventions etc., what else can one do besides just be there for that person, wish them well, pray for them and give them the best care one possibly can for as long as they are living. Like you are doing. We all know we can't change people, we can help them if they want help and hopefully they will want that help.
Best wishes for you and your friend.