She grabs you and pulls you through the mirror. You are in a room alone with the girl, surrounded by mirrors. She speaks: "Hello, you don't know me, but I know you. Your parents found my mirror before you were born. They realized what this was and broke my mirror before it could hurt their future child. Now you've freed me."
She grabs your arms and starts spinning with you. You grow dizzy. When the world reenters focus, you see kid that looks like you standing in front of you. You get pushed back and stumble through a mirror.
Back in your world, you stand up and notice you are the girl from the mirror. You look in the mirror and see your old body. The mirror shatters.