Of course, none of them know who she is, but people know that someone is killing Death Eaters, that Voldemort is searching for whoever is thinning his ranks, that there have been no survivors to her attacks, no words of what she looks like. She leaves no trail (she is thankful she is so gifted at memory charms, no memory of Charlotte Sewlyn or a pretty blonde in Knockturn Alley remain), and she works with brutal efficiency.