Sabrina wondered if they were talking about the stone she found. She wasn't close friends with Zoe Gibson (Jon's sister), but she knew where she lived and she did find the stone on Zoe's front lawn. Perhaps the stone really was her brother's. If that was true, then they were going to be a problem. There was a chance that they may find out that Sabrina was the one that took the stone. She couldn't have that. She didn't want them to spoil her fun.
So, she decided to make a wish on them. After pulling the wishing stone from her bag, she said "I wish ..."