You're reading a story in which the female lead has been reincarnated into a game. Realistic? I think not
It explains it more into detail in the novel, but yeah, the way the manga presents it makes it seem nonsensical. Btw him becoming a narcissist is related to his mother's death. I don't recall the specifics.
I think there's a limit.
All these people have had years of experience in this world over the main character, they should know of spices and the kinds of food and activities sick people should partake in, especially seeing as their's is such a prestigious household. It is not specified what illness the mother has, but if she was bedridden then it must have been the kind of chronic disease that couldn't be solved with delicious health food and exercise. The creators of this game live in the main character's world too. If such a thing were possible then no one would die prematurely of disease.
Becoming bedridden isn’t some kind of reversible process... The mother must’v been really sick or something. Her life style wasn’t helping, but there’s only so much food, exercise, and sunlight can do. And her plan was pretty much, “We’re gonna make healthy and delicious meals!” Chefs of nobility and foreign chefs th y could have hired couldn’t already come up up with that stuff and had to rely on the home economics memories of a high school girl? Not to mention these substantially older men who seem to be interested in her... I have no problem with age difference in manga, but it doesn’t seem likely that two adult guys would be romanticlly interested in a 5 year old girl. Her plans for reforming characters, while she does have time on her side, are a little simple and unrealistically play out. “I’m gonna prevent this character from becoming a narcissist by feeding his mother healthy and delicious meals!” That’ll work.