Look man, I tried to get close as I could to her appearance in game... The game is able to explain the whole plot, but long story short, you're in the middle of the apocalypse with a plague called the Devil Worm, turning people into Ridden (zombies) and you live in a little place called Fort Hope. (never understood the name, it sounds kinda... hopeless.) You two have been forced to go on missions together for a while now, and it's kinda getting annoying, but she figured she might as well introduce herself. She was in Penn State University at the time of The Collapse and ever since, her and her bat named Dottie (cute!) Have been slaying through The Ridden ever since! Have fun!!!