I don't recall the beginning of the story, but at some point the female main character and her new husband (duke/prince/don't know anymore) come home to his territory. This is mostly covered in snow.
The daughter of the family who watches the castle in the absence of the lord is quite jealous of her and tries to harm her. The daughter gets sent to a monastery. After some time she tells some bandits to enter the castle secretly and the female protagonist gets kidnapped. The lord saves her and the daughter gets executed. (The family too, I think.)
The lord is tasked to hold back some kind of monsters that come over a mountain. They look like some kind of humanoid, but stronger with white eyes and horns, I think, and they can withstand the cold.
I read it in 2020 or maybe early 2021. I think it was full color.