That's one long sword

You mean scissor.

why scissor？

Dr.E said:
why scissor？

Why not scissor?

You mean half-scissor that turn into a giant ass long sword

Dr.E said:
why scissor？

I haven't even watched this yet but I had a bout of fridge logic thinking about that earlier today. It's my understanding that the characters battle using super suits that double as uniforms. Uniforms are made out of fabric. And scissors are typically used to cut fabric. So obviously nothing but (half) a pair of scissors will allow her to grasp victory!

Or they could just be referencing the fact that uniforms are fabric and therefore ruined by scissors :P

Actually.... Her scissors are made with materials that can cut through the Life Fibers. It doesn't have to be a scissor shaped. Satsuki's weapon 'Bakuzan' is also capable of cutting the Fibers as well. Same goes for the nail that the Nudist Beach uses. Of course the symbolic meaning is as you say, that to cut a fabric, you need scissors. And the fact that her dad is a bit of a nutcase apparently