If you go to brainhospice.com you will see that, unfortunately, what your wife is displaying seems to be a normal part of the end stages of brain cancer. My dad's neuro-oncologist said that normally people start sleeping more and more and then one day they just don't wake up.
I am so very sorry that I am not the bearer of better news. If you have not already, call hospice and have them come and make you and your wife more comfortable as you go through this terrible journey!
Good luck to you and your wife. Tell her what she means to you, how much you love her and spend as much time with her as you can, even if it is just lying next to her.
I am so sorry
Suzy