Again, this was The Substitution Stone, so Karyn's wish wasn't granted the way she wanted it to. Instead, her wish was changed to "I wish Zoe was naked and desperately wanted to kill me."
Suddenly, Zoe was completely naked. It was just as Karyn wanted, except for the next part. Zoe looked at Karyn with murderous eyes. Then she jumped up off her bed and slugged Karyn in the face.
"Zoe, what the hell are you doing?!" Jon yelled.
But his sister didn't answer him. She kept on hitting and kicking Karyn. Jon had to actually grab her and pull her away.
"Get your fucking hands off of me!" Zoe yelled, with psychotic fury. "I need to fucking kill that bitch!"
Jon looked down at the still-naked Karyn, who now had cuts and bruises all over her body. She wasn't moving and Jon feared that maybe Zoe had succeeded in killing her.
But why would Zoe do that? It certainly wasn't what Karyn wished for.