How is she dumb? She did her best, and don't forget that she's also still a child who just happened to know some surface level information of the future. She experienced everything firsthand, hence prone to be traumatized by what happened as well. Can't she grieve? Is she dumb already just because she become a little mentally unstable or emotional for a while? Knowing some things doesn't mean you'll immediately become coldhearted or very intelligent like you want her to be. Remember that she did not transmigrate nor came back from the past as the 'adult' Sasha. She sees, feels, and treats everyone as a real living person and everything as her own life rather than merely a fictional character and story from someone's imagination.
Plus, it's funny to see how easy for you to say that 'she could've saved everyone' as if you did not witness how hard she pulled herself together to remain sane and take care of Estelle, as well as the two brothers, after being locked up for a long time, even though Sasha herself is already on the verge of breaking down. It's as if we're not reading the same thing, or you're just incapable of being empathetic and understanding of her circumstances.
Seems like these kind of realistic novels are simply not for you, so good bye. You probably just like those brainless revenge stories with Mary Sue characters.
