
Even though she is a concubine, has she never saw her husband's face?

Sometimes it happens.
An emperor takes in a concubine sometimes not because he wants her but for other reasons.
Like politics, her family a high Nobel family maybe gave her as a gift to the Emperor.
And he didnt refuse so not to alienate them.
Or he took her in as a condition from her family. If he wanted their land, resources, money, power, or something and they would support him if he made their daughter his concubine.
That's my guess.
That's why maybe she never met him since held no real interest in her and never met and spent a night with her. He just ignored her and let her do whatever she wanted that was limited.
She's a concubine in name only
How did the FL become the crown Prince's fiancée? Even though she is rich her father is a commoner right? Normally shouldn't the prince's fiancee come from a powerful family? Also why is the prince's attitude change towards the FL unlike the original story line? Is that because she is not the original Stella?
The prince's mother was a commoner. The fl's family welcomed her at the academy and they became close friends. So the two mother's wanted their children to get married. The fl's family is powerful, but more in a nouveau riche way, where her father became rich through business rather than noble inheritance. The prince has a thing for the fl because she was the one who comforted him after his mother's death and didn't make fun of his mother for being a commoner. I think in the original novel, they met much later in life and by that point he was jaded and she was shallow.