Karyn (that is, the original non-slut Karyn) watched helplessly as her body acted just like the slut that everyone thought she was. She was just going about, doing her homework, when suddenly, she had no control over her body, or even her thoughts. She could hear someone else's thoughts in her own head, which were in her own voice, but these weren't thoughts that she would ever have. She tried desperately to talk to the other voice or just talk aloud, but it was no use. She was a prisoner within her own mind, able to sense what was happening around her but unable to do anything about it.
What caused this was Jon's most recent wish. He originally wished that everyone except for himself and Karyn would think that Karyn was the school slut. But then he wished that Karyn would act like the school slut. He had already wished that Karyn would not think that she was the school slut, so obviously wishing that she would act like the school slut that everyone thought she was would be a contradiction. So the stone created two "minds" within Karyn's brain. The trapped one was the original Karyn, and the one in control was the Karyn who thought that she was the school slut. As it turned out, only the original Karyn was aware that her body had two minds within it. The "slut" Karyn didn't even know of the original Karyn's existence.