They had to save her. She was a princess of Equestria! Celestia's sister! They had to! There was no way they couldn't! If Princess Luna really was going to die without that piece of her soul, what choice did she have? What would Rarity and Applejack and Pinkie Pie and Fluttershy say if they didn't? What would her parents think of her if she was the one who failed to save a princess?