A cunning younger sister and an observer older sister—what is the ending that results from the actions of these two after their engagement is broken off?

My younger sister, who is two years younger than me, is a cunning and selfish great demon. She is always taking away my precious things. Even when I complain to my parents, they only tell me, "You're the older sister, so you must be patient." Eventually, I gave up on everything and began simply observing this cunning demon's behavior. Then, when I was selected as the Crown Prince's fiancée at fifteen, my sister complained as expected, "That's unfair! Why does big sister get to be the one!" But father said this decision could not be overturned. My sister began frequenting the palace and appealing to His Highness that she would be a more suitable fiancée, but... I simply continued to observe her behavior as usual. My engagement ended up being broken off because of my sister's actions... but what became the result?