"Alright," there's a hint of sing-song teasing in her voice, which should give Kate slight warning for what's coming next, which is Steph looking up at Kate through her eyelashes and adding in a suggestive tone, "I'll be a good girl."

It serves the purpose of both teasing Kate, and as a way to avoid the question. What they're doing after is a secret, and Steph is nothing if not sneaky.