After I read your comment.. You have a point. An 8-year- old kid who can create a new product, could do a business strategy...
That is way too much for a kid!!!... Like, kids cannot really tell the specific oddness of Tia but an observant eye especially by the adults will notice Tia's intelligence...
I guess the reason the adults did not suspect... Just my speculation...
1. grandfather might be a genius of his own... And thought that the education he has given to his grandchildren is effective to Tia.. This also shows he is not an attentive father to his children and maybe leave all the caretaking to his servants
2. Her father is way too loving of her, meant his cherishes her and not be critical of her.. and just shares his love of books..
3. Her aunts and uncles are not that observant of her.. Even though they are in close quarters... They are just minding their own business.. And Gallahan does not drag how genius his daughter was..
enjoy the story but why does no one talk about how she shows *waayyy* too much intelligence for an 8 year old (obv i know she was isekai-ed twice but the thing is that why is no one around her even a tiny bit sus? they all just acknowledge how cool it is and move on...)