My headcanon: Cozy Glow was not turned to stone, no one went actualy, they menaged to escape, leaving Cozy behind. She was angry, confused and alone, so embarrassed that she didn't even want to go home. Starlight started taking care of her, being her mentor, because after all Cozy is just a child, she needs guidance not punishment.
Bonus fact: Starlight works helping ponies and other creatures redeem themselves, sometimes daydreaming about be "the princess of redemption".















