Tensei Shitara Last Boss Kei Akujo datta!

I was reincarnated as Diana, a villainess destined to be the final boss, and I was living with the Ice Duke, with whom I was already in a political marriage, and his daughter, who feared me. My fate was to one day be defeated by my daughter's heroic lover—but I refused! I'll shower my daughter with love, improve my relationship with my husband, and aim to avoid becoming the final boss!!

The story of a quirky duchess escaping her villainous status begins in grand style★

(Source: Kadokawa, translated)