Im thinking, she was forced to marry that duke since no one wants to marry her. Why not ju...

Because the childhood friend is the third son of a baron

The father wants to use his daughter's marriage to gain benefit. Even if the duke is poor, at least he have the duke title. Meanwhile Claude won't get any title because he's the third son

Oh thats too bad. Hope that duke gets a karma. And that bish falls down the stairs and die. （￣へ￣)