The Devil Dragon's Substitute Bride

Her younger sister is dying and will not last without help. The cousin promised to the Dragon Duke refuses to go, takes a man who looks kind instead, and the family sends her in the cousin's place, as the bride handed over. The duke is said to eat people and to be brutal with everyone near him. The man waiting for her turns out to be good-looking, and after the wedding he indulges her and puts what he has behind her, so she climbs back up from where she had been left. The cousin's own marriage goes badly and her husband treats her poorly. Word reaches the cousin of how the girl who took her place is living, and the jealousy sends her out of her mind.