From the source:  
During the MLP staffers panel at Comic Con this year, a little girl went up to the mic and asked “If Sunset Shimmer had her own element of harmony, what would it be?”
 
Meghan McCarthy, writer of the Equestria Girls movies, decided to answer. She said “I’ve actually thought about this. And I think Sunset Shimmer would be the Element of Empathy.”
 
I thought that was such an awesome concept that I ended up getting inspired, drawing a messy pencil sketch of Sunset, hair billowing upward, hands open and welcoming, an expression of understanding on her face.
 
Cut to several months later. Equestria Girls 3: Friendship Games is released, and Sunset Shimmer truly proves herself as the embodiment of empathy in everything but name – represented beautifully through her transformation in the finale.
 
And so I dug out that old pencil sketch and decided to give it the full-color treatment, with Sunset donning her new form - this is the result! I hope you like it.