She was just happy that she had married her close friend and the one man every woman dreamt about marrying.
She did fulfil her requirements and was very kind to the little prince. But her dissatisfaction began to grow. That's because when she signed that contract there was a condition in it that there would be no husband or wifely duties between them. She was simply married to be a mother to the young prince and she signed on it.
She could have intimate relationships with anyone as long as they were vetted prior by the Bloodgarde. If she wanted to leave and start her own family she would be given a huge sum of money and an extremely comfortable life.
She decided to not only be the little prince's mother but be the emperor's genuine wife. But soon she realised she was competing with a dead woman. The emperor would constantly remind her to maintain their respected boundaries.