Katherine just came in and was looking out the window. Ryun asked her what she was doing and she said, "Im looking outside to make sure Emily didn't tell Stephanie to hide."
Katherine had just come in, after looking out the window earlier to see Steph and Emily playing in the yard, and going out to find that by the time she got out, Stephanie had left.
She wanted to make sure she was really gone and that Emily hadn't told her to hide.
It was kind of funny how well she knew her sister (Hate to say it, but that is something Emily would do...not necessarily to be mean but because she would think it was funny...Katherine of course is hyper sensitive and would freak regardless of Emily's actual intentions).