I'm super looking forward to this series!! I've been reading quite a bit of 'villainess' manga/manhwa for awhile now, and this one is interesting because she didn't have time to change the ML's opinion of her throughout childhood. He still dislikes her and it seems like she'll have to work hard to get him to trust her at all (curious about how she will pull that off).
Also, as a kid who loved writing stories when I was younger, I love that this isekai takes place in a place she imagined herself as well.
Those of you who are worried about there being elements of incest- I don't think there really is any. They are just step-siblings who didn't even really grow up together. The first interaction that they had in like 10 years is after the parents' funeral and they are practically grown up. If they grew up as siblings, I can see how it can be a bit uncomfortable for some (even if they aren't blood-related), but it's not like that in this story.