Her past is unknown, but what we do know is that she had a really rough childhood. In the game, she's found locked up in jail for killing a brotherhood soldier, and she no memory of doing so. She suffers from DPD and sometimes becomes another person entirely, (Her dead brother). However, Allison doesn't believe she suffers from any mental issue, put believes that her brother possessed her. Allison by herself is a kind person and doesn't like violence, however, she is really smart and is able to help the player make peaceful solutions.