User blog comment:IamJakuhoRaikoben/Chapter 457: Naked Battle, Review./@comment-4999650-20151019120400/@comment-25111584-20151019143958

Lucy was trying to stab one of the strongest Mages in Earth Land, a veteran of many battle, who had voluntarily turned her back on her. No way would have Lucy's plan worked, because she did not have anything at her disposal to work with. So she should have just let this chance pass and wait for a better chance. Maybe try to telepathically contact Warren (assuming Brandish cannot jam her). After all, Warren already knows about Brandish's location due to the Magic Radar, hence Cana's appearance. When one sees an opening, one does not rush in blindly. The timing is obviously important, but so is the action to be performed. Which is why I think Lucy's action was stupid.