Nia Liston: The Merciless Maiden

Overview

Rose Adel is the eldest daughter of a marquess. She absolutely adores her betrothed, the third prince Licht, and has devoted herself to becoming the princess consort he deserves. But then, she witnesses him spending time with another young lady and fondly gazing at her. While deeply hurt, Rose cannot help but wish happiness upon her beloved, and realizes the only way she can support his relationship is to play the role of evil villainess wholeheartedly! And with her fiance's older brother Richard offering his help, it's time for Rose to wipe away her tears and step up to the grand stage! Will Rose be able to make her mark as the greatest villain in history? (Source: MangaPlaza)

Source: AniList