Responses
The latter I believe
A bit of both I'd say. He didn't fall for her usual schemes like everyone else which got her interested in him which seems to have made her want to fuck him up more. Then line between just wanting to fuck him up for her own satisfaction and actually being into him got blurry and it turned into some kind of obsession.
So did the crazy bitch do all that because she liked the brother or she just couldn’t suppress the urge to fuck somebody up?