Whether they had the choice to kill her is irrelevant. It wasn't heroic. It is ludicrous to say that it was a heroic thing to shoot a woman dead in front of her child.
What did she think would happen? In the depths of PND who the heck knows. I find these flippant remarks along the lines of "she should have known better, and what did she think would happen" really disturbing actually, mental illness is not rational.