Character: sunset shimmer
Sunset Shimmer is a unicorn who appears in the Equestria Girls movie as the primary antagonist. She steals Twilight Sparkle's crown (the Element of Magic), leaving a fake in its place, and flees through a magical mirror. It is revealed that the mirror is a portal to another world, and Twilight pursues Sunset through it in an effort to retrieve her crown.
Sunset Shimmer is a yellow unicorn with a yellow-and-red mane and tail and green eyes. Her cutie mark is an eight-rayed sun, half red and half yellow. She has an arrogant attitude not unlike Trixie.
It is revealed that Sunset Shimmer was a former student of Princess Celestia who became impatient with her studies and began looking for shortcuts. Sunset seems to be an accomplished user of magic, and is seen using a teleportation spell identical to Twilight's.