User blog comment:Xilinoc/Ch. 580 - THE LIGHT/@comment-24113610-20140515082450/@comment-6812492-20140516194340

We've already seen Giselle use her powers to defeat a group of shinigami who blindly jumped into a fight with her. Surely someone saw her powers at work. It's not as if she didn't announce them to the world. :)

On the other hand, it's also probable that in the face of attacks that don't make her bleed, Giselle would happily cut herself and throw her blood...which means nobody could safely get close. Though I do like the idea of Tsukishima using Book of the End on her.