So Sade has "a thing" for happy couples, huh?
She cursed a man so he's forever a child, she scarred her sister (in more ways than one) so she can never be with anybody, she cursed the Duke so he can never touch Alice and finally she put Sharon into eternal slumber with a plan to wake her up when Alice dies to make her suffer. It's interesting that she went after Sharon and Alice instead of the man... It's either because he was already dead or he was the reason why all of this started. He either betrayed Sade or he was merely an object of her affection and since she's crazy witch she went full yandere mode.