Transmigrate into a Book! The Laid-Back Heroine Returns to the 1980s and Wins by Doing Nothing

Period Novel, Reborn, Not a Saint, No Awful Relatives

The female lead is reborn during her marriage and pursues the male lead. No saintly heroine, and no obnoxious in-laws. If there are any, she needs to stand up to them head-on. Especially no awful younger sisters-in-law or elder sisters-in-law. Other novels always have characters like that, and the heroine never fights back, which is so frustrating. Ideally, the couple also splits off from the family and lives on their own.