Jonnie sat down and looked at the stone. Then she had her wish. "I wish," she said, "that that woman had a teenage daughter as a child because she has a teenage daughter of her own, not because that daughter is me. Now, I wish I'd be back with my own family, meaning the one with Mom and Dad and Zoe and Mikey. While we're at it, I wish Karyn knew I used to be Jon."
Jonnie blinked hard--everything changed around her so she couldn't really look away. Things in the room changed slightly--mostly pictures, anything with her last name on it, and the layout of the room was now her old one. Visible out the window was the familiar scenery and bushes outside Jonnie's own room. Jonnie was at home again.
So Jonnie had fixed it as much as she knew how.
Except for the one big problem. Jon was, for all practical purposes, stuck as a girl. Since the 'daughter' wish had happened another way, she could change back to a boy--but then she'd be stuck groping breasts. Which wouldn't be good.
At least, everything else wasn't caught up in wish trouble. Jonnie could become any kind of girl she wanted--popular, unpopular, the same as now, straight, lesbian, as attractive as she wanted or not. She could wish for a car and a new computer like she wanted, or she could wish for something feminine like a new wardrobe. She could try to act like a girl, or she could wish that everyone was happy with her acting like a guy. She could, really, do anything--as long as she stayed a girl.
[Author's note: Sometimes wishes and threads get too complicated. This one is a simple effect--Jon's a girl, with no other details fixed. Do with it what you will.]