Manhwa that starts with the emperor poisoning the empress with their child in her stomach

The king poisons the queen with the help of his mistress. He told the MC that he accepts their child to ease her doubts, but made her drink tea without her knowing it's poison which leads to her death. Then the MC's soul was transferred to a girl, then she seeks out a duke(?) and introduces herself as a person of the queen that died, and asks him to marry her to get revenge to the king. They got married and she attended her own funeral. That's the last part of the story I've read. I forgot the title.