Why doesn't orielly demand answers from Bush the same way he expects the same from this one grieving mother.
He was not demanding aswers from her he was just going to have her on then hear her out. She cancelled end of story.

And why does the fact that she already met with Bush invalidate her current protest? 
It really doesn't you have a point. It just reflects a bit on motive. All you have to do is find out who is propping her up to figure out what the motive is. I really have to wonder who contacted who in this case

 They need to wheel someone out there on life support and the whole republican party would come flying in from everywhere with some new law to pass. 
Dan I think this would be an excellent opportunity to meet with her and show some humility regardless to fact that other widows might make the same request.