Akuyaku Reijou wa Danna-sama to Rien ga Shitai!: Suki Katte Yatte Ita no ni Naze ka "Ou Taishi-hi no Kan" Nante Yobarete Iru no desu ga

When I woke up, I found myself in the world of a dating sim, where the heroine had met a bad end. I was reborn as a villainess married to the crown prince! My marriage is on the rocks, and I've decided to leave and start a second life - right when I decide to do so and begin managing my territory, for some reason my husband's attitude changes... This is a story of a villainess's struggle to become a happy-go-lucky woman in a world of schemers!

(Source:MangaPlaza)