Yeah. The problem with Peri isn’t that she’s a psychopath, it’s that Xander (Who despises Hans for his lack of humanity) and Corrin (Who dislikes killing people, and is portrayed as kind to the point of naivety) are fine with having her around. It’s blatantly OOC for the both of them, Maybe instead, Xander wants to help rehabilitate Peri, rather than enable her.
Or maybe make her a recruitable character like Shura in Birthright. After defeating her troops, you’re given the option of murdering her (and getting a reward) or recruiting her. Maybe Xander’s replacement retainer could be Charlotte instead. She’d definitely wanna get close to the Prince.