Serini acting all casual after kidnapping them is honestly being played more as a joke here, if on top of expositing this pretty dark backstory she also had to brood about having to stray into the gray areas of morality for the greater good, that would kinda make the comic way too moody. Characters acting all casually in life threatening situations has been a running joke in this comic, adventurers especially are consistently portrayed as taking all of this in a very "business as usual" manner. I mean, even the paladins seem more annoyed than fearing for their safety here.