Very Bold Move

This short story brought up those simple but unsolvable questions--what is justice? who should be the one to practice justice? Emotionally I can see why the woman made this choice because she has an unswerving faith that this man in front of her murdered the love of her life so she can not let him get away with it. Very bold move. But objectively, this seemed to be an unwise choice. Killing the murder cost her own life. How's the deal?