Everyone does mistakes, and even Bayonetta isn't an exception. It may be that the weak Fly-mutants are no match for Dante and Nero, but for female enemies they got some "special techniques" in stock. And so it happens fast, that the overpowered Witch got suddenly overpowered and learning more about the "special techniques" of the Fly-monster. And eventually, while one egg gets lay after another deep into her body, she realizes her failure and admit her defeat. Too bad, that this was her last mistake, because she will be busy now, being a productive incubator for all her lifetime, and this can be a long time, especially if you are a Witch, right?