The unicorn tried her best to come up excuses that it wasn't her who killed the fancy stallion. But her mind had different plans. It just kept hammering on the fact that, even though she had changed, it still was her who set the fangs into his flesh and drained him from all of the blood. Rarity needed to make up for it in one way or the other. And there was only one way for her that would make that a possibility. There was just one way she could possibly ask for the redemption of her tainted soul and beg for forgiveness.