what just happened?

It could be Nitori giving an upgraded optical camouflage suit a test run.

Great Scot, gravity has rebelled!

i think I've been playing to much metal gear solid; I've got the exclamation point chime and alarm music stuck in my head now

I'm thinking this could be a Mario joke, where took damage and shrunk in size, her hat remaining in place for a moment and her bloomers becoming oversized. Why the broom dropped? I dunno. Maybe just from being surprised.
Or it's something invisible pulling pranks.