I didn't get that impression, she's the type of creature to seek out fun and amusement, she likes trolling people. Like how if you give her a different name than what you said originally, she forces you to say the first one, some people view it as some sort of power play but I interpreted it more as she's just fucking with you.
Similarly with the whole apocalypse situation, maybe I'm just messed up in the head but I totally would tease people about it in her place too because its funny to see people freak out. Once upon a time when I was a kid in high school there was some sort of a shooter in the area close in proximity (dude was just angry at girlfriend leaving him so the dumbass just shot up some cars, nothing important) and everyone in the school lost their shit, some were crying, some looked like they saw a ghost, to me it was just amusing finally something interesting happened. I would tease people about it all the time, now granted that's not the same as a world apocalypse but maybe she isn't that bothered by it because maybe its outside of everyone's control or maybe its not really that bad or maybe its really that bad but in that case why not have fun instead of despair.
Besides, Heloise deserves to be happy, and if she wants more apocalypse kids then she should have more. World has already gone through one period of naga messing up reality and everything turned out fine by the end, couple more of them couldn't hurt if Malice didn't insist on being a single child for now.