Sarah sat in the water, a mere spectator to the gladiatorial match that was taking place in her head. Goth vs. Cheerleader. A battle that raged for an eternity, so far as Sarah was concerned. In the real world, it only took seconds, as both portions of her mind collapsed in exhaustion in time for her to hear someone say the words "You're my slave." With nothing left of her mind to argue, she simply accepted this claim as fact, shook her head, and looked for the person she would now call "master."
Morganna smiled as her doppleganger obediently stood up, bowed her head, and walked to the shore. "That's better," she said, patting her new servant on the head.
At this point, neither girl was aware of the powers that the magic rock held. The original Sarah was a mindless slave, and when Jon became Morganna, his memory of the stone was erased. Morganna began walking towards the park exit, and silently waved for Sarah to follow, which she did. Morganna was about to take full advantage of her new slave.