The merchant's daughter was originally his wife, but the princess took advantage of her and turned her into a concubine.
Who said that the princess is a golden girl? She is just a humble merchant girl, and she will be trampled under her feet by the princess? What if the princess becomes a princess whose country has perished?
In the old feudal era, a heroine with a low status would live a miserable life at first. There was no way around it. After all, the heroine in the original text was an ordinary person in her previous life. She could not be so powerful that she could influence the ancient society all of a sudden. If there was a major industrial reform, she could only rise after experiencing all kinds of hardships and setbacks!