I had thought she was wearing risque Choujuu Gigaku clothes for a moment but that's entirely my mistake. This is some variant of the Gensokyo sleeveless hakamashita.
I find it kind of funny that delinquent-Kyouko, who is saying something specifically meant to provoke people, managed to spectacularly accomplish exactly what she wanted.
This may be me being a little nitpick-y, but I wonder how great the provokation in Kikiriri's picture would be if Kyouko was flipping the bird? It might be a nice cherry on top of the ice cream here.