The Madison children took their morning showers in age order.
Zoe had been in the shower when suddenly she was completely dressed and ready to go. Since she hadn't heard the wish, she was unaware that she was now the oldest.
She paused in the hallway and went back to her room and grabbed the wishing stone off the dresser. Since she was the oldest, their grandfather had sent it to her. She stuck it into her bag and headed off to meet her best friend.