Silla Heks is one of the many members of the Heks family. She is related to Stina Heks, Vika Heks, and Timkin Heks.
Silla Heks noted all kinds of interesting observations about the way her alicorn had affected her emotions. She also thought that alicorns have a special way of inflicting their feelings on others - both good and bad.
This is a legitimate character that Mr. Forkle talked about in Exile, pg. 505 hardcover.