When you say Sakuya you mean Flandre right? I don't think Flandre realized she used her power until just now. As for the no spark it must this artist's rendition of of Flandre's "eye" crushing power.
I did mean Sakuya right behind Flan but now I say both since Flan is showing that surprised expression by here cheek.I am going to agree with you on this. The question i have right now is does Remi know that her hair is no more