Do I need to wait to get married until the engagement is broken off?

One day, the villainous young lady Luria realizes she has been reincarnated into another world. She cannot accept that her engagement to her beloved Crown Prince Satarin is being broken off. After all, she insists that she can make Prince Satarin happier than the heroine! She threatens her father—or rather, cajoles him—who was the cause of delaying the marriage. If she can just complete the marriage before the heroine appears, that would solve everything. With this thought in mind, she puts her plan into action. *Also posted on other sites.