also I kinda understand Karina's decision not to accept Hexion's proposal.... marrying him isn't the solution, she was assassinated in the past (for whatever reason) when she's sent off to the grand duke, remember? so if she's just marrying him again now then it would be just the same. there's no guarantee the duke won't try to kill her after youngest daughter born, there's still no stopping them to want to get rid of her.
So something must be changed, either completely change the family's attitude towards her or cut ties and run away from them, and live as a commoner.