How do I resolve a rivalry with my wife?

How do I resolve a rivalry with a character, or specifically in this case, my character's wife? I bagged my character a duchess as a wife (and not matrilineal) which means that the first kid produced will be heir to that duchy - and since I have elective, I can easily set him up as my heir as well. Good, right?

Except that now they're rivals, the character's getting old and I don't have the time to resolve this in a lengthy manner. Help?