I have a deja vu feeling thinking about this and am not sure, if i have noted this before... but... schroedinger would not go into a crime szene without these full body suits. Her Bosses just wait for her to make a mistake, and that would be it. BUT its a comic and she just pops up in this one panel - there are already enough characters around without changing the costumes and hairstyles.
I will never explain this scene within the comic. But i imagine, that the lady knows this butcher shop pretty well and worked in it for some time to learn the regularities of this business. She quickly shot the workers and then went havoc on them, which she did not particularly enjoy. Barbera is right to be jealous and would have done a way better job. Buuut Barbera, Jaune and Gabriel were busy with Misses Joyce in the previous chapter at that time.