Wow. I pitied that sister so much. Give me back my feelings! Sure, what the brother did was dickish and the sister is the result of the bad influence of the parents, but as it turned out fleeing the way he did was his only chance to escape! Would he have stayed to argue, those people under the secret leadership of his sister would have had their way with him.
Now I also know way she stayed so calm. I thought she was half heartbroken, but she calculated he'd be back. At least he realized it was her and how dangerous an scheming she is.
...but wait....That also means she knew he'd run. This implies she knew he wasn't okay with marring her, too. Since when? Since when did she plan to take his freedom away from him? Holy shit! That much at an age of 14. She is the devil!
As soon as she learns her plan backfired she'll be on him! And the worst, the whole village will blame him for her disappearance, too.