Karyn was waiting for Jon to show up. What was taking him so long? She hoped that he hadn't gotten into some kind of trouble.
Then her doorbell rang and she became relieved. When she opened the door, however, her relief changed to shock. Jon was standing on her front porch with Alan (a friend of their's), and they were kissing! And Jon was dressed like a girl, and he acted like everything was fine!
"Jon! What are you doing?!" she yelled.
Of course, Karyn didn't hear the wish that Sarah made, so Sarah must have made a wish that Karyn would notice when things changed. Sarah wanted to take Karyn's boyfriend (who she thought was Jon) away and also rub it in. But Sarah didn't know that Karyn and Jon were just friends, nothing more.