Emotionally unstable girl, with an emotion-dependent ability.
Alison discovered at a very young age that she had a special ability. Some would see it as a gift, others would look at as a curse. Her parents knew early on that there was something different about Alice. It was discovered that she had powers that were linked to her emotional state. Different emotions triggered different abilities. For example, intense anger will give her more violent or destructive abilities (strength), while fear or desperation would allow her to use powers to help her escape the situation (invisibility).
Alison's parents tried desperately to keep their daughter's power a secret, punishing her whenever her abilities were used. But of course, you can't control your emotions. And it seemed the harder Alice tried to hold it all in, the more emotion she began to build up inside of her. Afraid that they had lost control, her parents kicked her out of the house when she was fifteen years old, tired of living in fear of their own daughter and what she might do. She was forced out onto the streets and did whatever she could to get by which mostly included stealing. It started out as stealing food in order to keep her strength up, and eventually turned to something bigger. Like jewelry, cars, and eventually banks.
In the midst of all her trouble, Alice was finally starting to fit in somewhere, and even found friends. She was finally starting to feel happy again, and didn't want to have to keep lying to her friends every time she 'disappeared'. So she revealed the truth about herself to her new friends, and they did not take it well. In fact, she vaguely remembers them calling her a 'freak', and telling her to never come back. The even threatened to reveal her secret and crimes to the police if she didn't stay away from them. So, it seemed Alice was back to square one in regard to finding a place to fit in again.
She'd heard rumors of a place that was made especially for people with unique abilities. After some more research, she was recruited and enrolled into the Xavier's School For Gifted Youngsters as a new student, hoping to learn more about her powers, and how to control them. She has been there for a year now, and has greatly improved, but she's found that she can't control herself as well around certain individuals in school. But she's working on it.