MYOMYOHEE

https://www.mangaupdates.com/series/yfucazr/how-a-time-limited-villainess-gets-revenge

Berry Swanton doesn't want to marry her fianc without ever experiencing romance. Dreaming of love like the heroines in novels, she dates several men in high societybut none of her relationships last more than a week. Labeled "the girl who always gets dumped" or "the one-week romance," Berry, acting on impulse, even seduces an innocent baron's son fresh from the countryside. She plans to seal a one-week romance with a kiss at a shipboard party only for her fianc, just returned from studying abroad, to suddenly appear and confront her about her affairs.