"No! You don't know how dangerous this thing is!" the older Sarah yelled, as she struggled to keep the stone from her younger self.
"Give it to me! I need it!" Sarah yelled. "I deserve it!"
The older Sarah's eyes went wide. She had forgotten how egotistical she was. Before all those wishes (and mistakes), she really was a bitch.
The Sarah from the future did her best to stop her younger self, but in the end, the teenage Sarah won out. She stood up triumphantly, holding the wishing stone in her hand. And then, with a big smile, she said "I wish ..."