Bubu, Eodikkaji Ganeunghae?

The Song family's true biological daughter appears, shaking Ju-Ha's world. Seeking an escape from an unwelcoming home, Ju-Ha embarks on a series of blind dates until she meets Sa-Hyeon, who boldly suggests setting a wedding date within minutes of their first date. Just as Ju-Ha starts to develop feelings for him, her cunning younger sister—who has already taken everything else from her—declares her intention to marry him instead.

(Source: WEBTOON)