The book 'Marry a Noble Wife in Substitute' meets your needs. The female protagonist traveled to ancient times and was robbed of her good marriage by her eldest sister. In the end, she was forced to marry the son of the prince who was suffering from a strange illness. The prince was originally married to the main wife, but because of her health, the imperial edict granted her marriage to the female lead. The female protagonist won the heart of the prince through hard work and saved the fate of the family before she traveled back to the modern world. I hope you like this fairy's recommendation. Muah ~😗