A lot of people remark that Shiraori isn't human but one thing the web novel just brought up and I found interesting was how Ariel asks her friends to be patient with Shiraori, since she's just a child who's still figuring out how to relate and interact with others and the fact that she doesn't understand this herself only prevents her from objectively assessing her actions and understanding when she takes things too far (which is always, forever) so, she usually just escapes from and justifies all her actions, my favorite catchphrase of hers in the novels is "If you think about it, you lose!" coupled with many of her monologues creating a justification for her aggression out of minor details or shifting the blame to her victims.
This to say that Shiraori is like one or two years old, she was a spider after all, and while she does have a lot of knowledge from her "past life" most of it is vague nonsense D made as a cover story, like she being a 16 year old stock broker with no parents; rather than actual memories
Hell, I'm pretty sure her most detailed memories from D are MMO facts, rather than any social skills, empathy or human interaction; which to be fair is applicable to us bunch, but hardly useful to a child.
So with that in mind, what we're seeing is Shiraori's character being created by single moments which come to define her; such as her developing a trauma to the monkeys, from which she still runs away as both a demon lord and a god later on, her obsession with power and her "The weak are food and the strong do eat" mentality, which warped what little common sense she had to begin with.
And as a final nail in the coffin [Taboo] also lightens the weight of any of her atrocities, not because the skill itself changes Shiraori's attitude but because once you unlock it and understand how the System works, any killing becomes a net positive for the world which only makes the prospect of farming humans all the more enticing, since not only is she neutralizing threats, which prolongs her life but she's becoming stronger, which prolongs her life and also she's contributing to sustaining the world, which prolongs her life.
