I recommend Princess Ning He to you. The plot of this book matches the information you provided very well. The female protagonist, Princess Ning He, had a moon on her forehead. After she was killed, she was sent to another country for a marriage alliance. She was respected by the people of this country and became the favorite concubine of the country's ruler. Her marriage also involved the interests of the country. I hope you like this fairy's recommendation. Muah ~😗