Surely there will be a screwup on Petras part from having gotten afflicted by Subarus mindset of "If things goes to shit, I can always just die" after reading the book since the Subaru in the book was before he made the bet with Roswaal? We have yet to see her negatively impacted by it aside from outside sources like the witch chasing her and I refuse to believe she'll end up just having a Subaru tulpa.