An Unknown Marauder?

Marauder's Era fic. What if there was a member of you didn't know? Why isn't her name on the map? James' twin sister was just as much of a trouble maker as the other four. I posted this originally on quotev and decided to move it here. Sorry I kind of dropped this story but am rewriting it. Spoilers for Harry Potter. All of Harry Potter belongs to J.K. Rowling. Rated T just in case