Sunset is the daughter of Princess Celestia who got turned into a human by Fausticorn and until she learns to love and get that love back she will remain a human.

Here is the cast:
Belle - Twilight Sparkle
Beast - Sunset Shimmer
Maurice - Spike
Gaston - Flash Sentry
Le Fou - Snips
Mrs Potts - Rarity
Cogsworth - Applejack
Lumière - Rainbow Dash
Babette - Fluttershy
Wardrobe - Pinkie Pie
Chip - Sweetie Belle