Back has always seemed a bit out of control on e she's mad. and she's still young as Aer puts it. Which means they can be easily influenced to the things that happen around them.

As of now, she's just thinking as a person who is mad and plotting revenge on someone who wronged her. Whether she be serious or not, it's something that does run in someone's head. Whether act on it or not depends.

Plus, ha know. She did kinda get possessed by a fiend, and now currently has a bunch of voices in her head xD

Usually that means insanity, which usually can turn into a dark side