Honestly, even if she hadn't realized it on her own, the fact that Miko has twisted her expression into a mockery of Peridot's and is currently lip-syncing clumsily along with what she's saying would probably be a good indication.

Then she literally actually stomps her foot. "Fine! Have fun with your weird nerd crap, I'll be upstairs having a life!"

She stomps into the kitchen, making a point of being as LOUD AS POSSIBLE about getting a glass of water, because if she has to do this now to maintain the illusion she set up, she's going to be annoying about it, dammit.