(except for that incessant niggling voice that says "maybe she just wants you to think she's sorry and she's just using you for more")
I would pay a lot of attention to that incessant niggling voice if I were you. Did she do any more than apologize? Did she say she will not behave that way in the future, or otherwise suggest how she is going to make things better? From everything you've posted, she sounds self centered, manipulative, unpredictable, and inappropriate. If you really want to give her another chance, I'd say proceed with caution!