By no means am I a psychologist or your "wikipedia warrior", but sounds like a sociopath for sure.
Best way to leave her is to disappear and ignore her-- cut it off cold turkey. The blinds will slowly lift for you and her true nature will appear.
Get an app that allows you to save txt messages, and save everything she does, while ignoring her emotional blackmail toward her.
Show no emotions in your responses to her-- it will drive her crazy. Be succinct and specific with no emotions.
