Please Cut My Hair

After the princess sent to another kingdom for a political marriage dies of old age in the enemy land, she is reborn on the day she was betrothed. In her previous life, she spent forty years transforming a barbarian realm into a land of ritual and refinement, only to be condemned as a "traitor" by her homeland on her deathbed. Reborn, she faces the barbarian prince who has come to seek her hand once more and cuts off her hair before the court. "This time, I've come to destroy your kingdom." She chooses to marry into the weakest barbarian tribe and uses the knowledge she gathered in her previous life to overwhelm them with a civilizational leap.