User blog comment:Xilinoc/Ch. 580 - THE LIGHT/@comment-11446176-20140514110357/@comment-11051098-20140514163325

Well, I have no idea what she did to Bambi as it was hidden from us. Giselle confirmed that her blood upon contact with others, turns them into zombies of her will. I figure that's what happened to Bambi that scared her, losing control over herself.

That or getting killed, but what Giselle said about them going to take care of her doesn't quite match killing her, I think. I find the first option most likely.