User blog comment:Xilinoc/Ch. 586 - The Headless Star 5/@comment-4026406-20140625164406/@comment-11051098-20140626134745

After Bambietta was defeated, Giselle said to her that they would be sad if she was gone. Seeing as she can only turn dead Quincies into zombies, I suppose she might have killed Bambietta and then zombified her, to "keep her".