"Why? Shouldn't she be in my room, since she's a version of me?"
"No," replied Jon's mother. "I used to be a kid once, and know other kids. I know what you have in mind. I'm letting her stay here because she's a version of you, but I don't approve of you going out with her. It's almost like incest."
"But Mom---"
"No 'But's."
Jon was shocked. Had he worded the wish wrong? Hmm... he had wished that when he tells people Jonnie was created by magic, they'd think it was completely ordinary... That was it. All he had wished for was to be able to explain Jonnie and be believed. He didn't wish they'd approve of her being his girlfriend. Obviously, his mother didn't like the idea of Jonnie being his girlfriend. He could wish that up, but there were even more ways that could go wrong.
Eventually Jon decided not to make more wishes. He needed to try to get the original stone somehow, anyway, and maybe talk things over with Karyn... though Jonnie was pretty good company too.