There are certain rules to international politics that Hanna must respect, because she is a princess and the commander of an army. Most of the rules don't give her trouble: don't invade needlessly, don't mercilessly crush anyone, don't shoot your own people. Being commander of the Dellian army involves a great deal more public works and horse training than fighting, and she likes it that way.
But when she sees the young Queen of Monsea for the first time, Hanna deeply regrets don't get romantically involved, because as sensible as that advice may be, it is going to make her stay in Bitterblue City very uncomfortable.