Spank her

You can't resist the invitation, what with her ass pointed outwards like this. You rub your hands together, walk over, and start spanking her exposed behind until it's as red as her face is.

* smack *

* smack *

* smack *

With every slam her asscheecks give an appreciable wiggle while the girl lets out a muffled squeel. When you're done, you give her butt a good grab. You can feel how muscular she is, even if that didn't prevent all the wobbling.

Judging by how red she is all over now, you contemplate whether she's learned her lesson by now.