
This should be an isekai, the woman's the MC.
The age gap is what you see, he's a kid and she's at least a teen, so they're at least five years apart from each other if not more.
In a few words, she read about the boy in a novel and felt sorry for him since he's the villain in that story, if I recall correctly. I don't think she died, she just woke up in the body of a maid working in the ML's parents house, and she's his only friend and supporter.
With time the kid gets more and more fond of her, not before trying hard to keep her far and make her hate him, until it turns into love after some years.
It's a good read in my opinion, I really liked they're relationship while he was a kid, but it turned less interesting once he grows up because the FL is a bit of an idiot.
I would like to read it, but I see a small boy, I want to know is there like a big age gap?