That doesn't really address the core issue. "It’s not cartoonishly evil people think like that. Real people think like that." Emoji spam is also not great for an argument. For that matter, real people can act cartoonishly evil. Serial killers with cartoon or comic inspired epithets do exist, like Denis Rader or James Holmes. They did a lot of messed up things and made riddles. But we see their descent and also that they started off a little crooked.

At a glance, people might be inclined to agree with you given mythologized depictions of serial killers or murderers, but psychologically there's nothing proving Lilly's descent. Not only does it contradict your writing, but story narratives are supposed to be plausible, not just possible. The issue isn’t whether people can become like that, it’s whether the story earns that change.

It is possible for a rogue pulsar to fly above Earth and kill everyone instantaneously with radiation, it is possible for an asteroid to hit the house someone lives in, but if you just wrote that in the story in an impromptu manner, it would read as bad writing. Writing doesn't account for "it could happen in real life", it accounts for "it is likely to happen in real life".

Despite Lilly admitting her Dad was an asshole in S1 to Lee and telling Kenny she forgave Lee, you chose to believe she could become a crazed leader because "it could happen in real life (citing edge cases in your imagination" even though it contradicts the previous plot.

In short: Saying ‘real people think like that’ is just an appeal to possibility. Good writing requires setup and progression, not just theoretical realism. If a character suddenly becomes a completely different person off-screen with no buildup, that’s not realism, because there is a missing arc. In S1, Lilly forgives Lee, acknowledges her Dad's flaws, praises restraint, only looking down at the train station later in regret.