I love the idea!
That would have been so dope!!!
She's already shown as a child calling the praying mantis (presumably) disgusting. She views him as the praying mantis. And we saw her bringing down the rock as a child. I think she shines because as much as she tries to hide and deny it: she's the apex predator, not him.
I dont think there is a way for her to be more psycho than him, unless in that timeline she does not love her brother. Cause we see in this one she does love him so she does not have anti social disorder like Inseop
She kills the praying mantis, she kills killers, bad things. She does love her brother which is why I think she'll kill Oh Inseop (he is the praying mantis). Oh inseop kills indiscriminately to get the object that shines, he even killed his own sister for a pen. She will kill to protect her brother. Her cousin was lucky the cops saved him from her (he did deserve to be beaten to death tho). I think once she kills Oh Inseop she'll find murdering those like him justifiable. All this is show in their childhood interactions with insects. I strongly believe it's foreshadowing.
I don't think she ever will find it justified, does not seem to align with her personality. Until now she never managed to even cut inseop. She is a normal person psych wise, she has empathy and love, she doesn't suffer from the same mental issue inseop does. Inseop totally lacks empathy on a pathological level that you cannot achieve if you are not born with that mental condition. That she will probably kill him we all know, but to turn into a psycho like him is unlikely cause you need to be born like that.
Okay this is such a stretch but in an alternative timeline I lowk want her to break and become more psycho than inseop but is better at masking / hiding it and even hiding it from the detective and the final chapter is her seeing someone as an insect like inseop does (like if she remains a teacher she sees her boss as an insect) then it ends but like she’s kinda learnt everything from him