"It would make your life easier too if you cooperated." Was really all Marty could say to her, she had clearly made her mind up about this situation and her place in it. It was going to take something much more than talking to change her mind about anything - and he briefly wished that he had some kind of superpower to show her he wasn't lying, though the way this conversation was going that would probably end up as him lying too.
He nodded. "They're trying to figure out a way to send us back from this reality to our own. I can't really say what will happen to us if they never find out how to fix this - but you can help us. When you're ready, of course." When she had her powers, if she had powers.
"It's not safe out there, not even if you just went to school and tried to live a normal life, you've missed out on the entire history of this world. You would stick out and draw attention to yourself and the rest of us." He paused. "You could start by reading some of the history books they have here, it's fine that you don't care about Hawaii or the Towers, but they are facts to the people who live here and if you don't know those kinds of things they will know you're not who you say you are."