
ok so maybe just maybe, she is the real empress.. remember, something happened 2yrs ago that she doesn't remember happening in the novel.. but she have fragment memories, and somehow maybe a spell keeping her from remembering what happened that day.. at the same time that same empress became lunatic and tyrant.. same timeline.. she met and forgot something then she became someone she wasn't.. Im speculating that she was sent to be reborn in earth (the one who live as a office worker who loves novels).. and someone else posed as the lunatic and tyrant empress.. she without memories think she's originally from earth and was only likes reading novels and coincidentally read the story about her past life.. but somehow, afyer waking up she returned to her past life (being empress)/ due to the protagonist magic.. during the festival the protagonist saying "she has returned" it means she was originally from that time and place.. I'm speculating that the father of the protagonist died somehow or was pushed to a certain situation where he needs to turn back time, (maybe to save himself) and due to that the empress who is sane and reborn to earth was also returned to the same time.. but without memories of herself as the true empress..
dont hate her if she's acting like a child even though she's 18 inside..for starters, she didnt have a proper schooling since she was cage in that cabin.. she wasn't able to interact with other people and the only book she read is that encyclopedia she mentioned.. she was abused and traumatized does for sure it affects her mentally.. seeing as how she is doing her best to avoid that same incident to happen, is quite amazing already and her being amaze and slightly ignorant with everything new for her is understandable.. just see her the same way as the little mermaid when she first set foot on land.. eventually she'll learn..
not to mention she doesn’t keep her brain, it goes back to before development/puberty so anything she learned and used to mentally mature is probably gone until after puberty.
But it’s isekai so I don’t exactly know how those mechanics work lmao