I think she probably knows it's not you. Not that I am suggesting this at all--don't do this--but I would bet if you said "I'm moving out and moving on with my life, let me know when you file," she would freak out and say slow down here.
I have a friend from back home in the big VA who has been very supportive of me fighting for the marriage. She always says "Well, put yourself in his shoes, what would you have said, what would you have done, etc." And when I can do that, it makes sense, I understand H a little bit better. But not fully because I don't live his life or know his thoughts.
I think your W knows you are there and while she may not appreciate it outright, on some level she does.
I think she'll snap out of it, but things with her family will have to settle down first I think. I think it's very difficult to live while you know someone you love is dying.
