I think she's a psychopath, too, so that explains a lot of JA's usual demeanor, but my sister (with BPD) had that effect on folks, too. Back in school, whenever it would ever come up that my sister and I weren't getting along, folks would always say, "But your sister is sooooo nice!" They couldn't imagine her angry (ha!).
She was spectacularly nice, and I love that about her. Unfortunately, she also turns into the Tasmanian Devil (her nickname since forever)! Like really, seriously effed up, beating me up Tasmanian Devil. Over not handing her the remote fast enough or something weird. It's a Jeckyl and Hyde thing, that disorder.
I broke her nose once, as a senior, in self-defense. Then she stopped beating me up
It's absolutely crazy living with a Jeckyl and Hyde, and folks can't read them from their normal demeanor. They have two different personalities, practically. I'll take the regular part any day
But that's not how they are, very unfortunately.