"I wish Karyn was the type of girl who wanted sex all the time," Jon said. Suddenly, the stone glowed, taking him by surprise. "Wait, why did it grant that wish?"
Just outside Jon's house, Karyn paused for a moment as the changes in reality turned her into a nymphomaniac. She still loved Jon and wanted to spend the rest of her life with him (because of an earlier wish), but loving Jon didn't quench her thirst for sex. Jon couldn't give it to her all the time, unfortunately.
So, as she walked away from Jon's house, she thought about who she could fuck. Everyone knew she was a slut, so finding someone wouldn't be too difficult.