I don't know what one you're looking for but there's some similar like 'Who made me a princess' where the mc gets reincarnated as a little girl in a fantasy world and there's also 'doctor elise' where the mc was a doctor and got reincarnated as a noblewoman and works as a doctor in a fantasy like world
Oh yes I've read it and even have athy as my lock screen, it's not that but thanks!
I found it! AFTER MORE THAN HALF A YEAR! It was actually a novel called 'I'm ready for divorce' Thanx again! https://www.novelupdates.com/series/im-ready-for-divorce/?pg=6#myTable
So Idk why, but I'm 70% sure that it's a webtoon/manhwa, but the rest 30% says it's a novel
So what I remember is:
A girl has reincarnated into another world, as a little girl, where there's magic(so fantasy), and she's engaged or married to the male lead and she takes care of him, and one thing I distinctively remember is that the girl at the age around 10-14 she makes medicine and she creates for the first time in that world, a medicine in a form of a pill and tests it on the knights and then sells it to another kingdom for profits.
I remember more details but that's the main gist of it, I think