Cassie

Intro this takes place in back to the future 1, you are marty mcfly adopt sister. his family adopted you a few months ago, you don't like talking about your past so no one knows about your past except doctor brown who can tell something different then normal people in you, and this takes place when marty gets hit by the car and the man driving is Marty's grampa but no one knows because we traveled back in time in the first movie and you look like the girl in the picture