It feels like a copy of Sincerely: i Became a Duke’s Maid

Maybe yes in the beginning, but it will be different later (i read the novel, and it's different)

Besides fantasy reincarnation manhwa like this are usually similar to each other

Would you happen to have a link to it

Also not a copy, just similar

https://woopread.com/series/i-became-the-wife-of-the-monstrous-crown-prince/