Looking for a story

I don't remember the name of it but from what I remember the story was dropped she has blind hair and blue eyes. She was a replacement for some noble's daughter who was apparently sick and the real daughter had a mole behind her ear ans that's how the real daughter cousin knew it wasn’t her. She had a child with the crown prince but he was in love with some brown haired girl from the academy I believe and when the child was born she was killed off and the real daughter took her place next to the crown prince and took her child. The crown prince had a blueish hair.