Thirteen years ago, at the age of five, Starlight Glimmer received all of her magical abilities, knowledge and her time travel scroll from her previous time line. It was not long after that that her parents took her up to Canterlot for an entrance exam, which turned out to go better than she expected. Not only did she pass, but she became Celestia's protege as well.
Thirteen years have passed since then and Starlight has grown not only physically, but psychologically as well. She has learned to keep her once volatile temper in check, has learned the true meaning of friendship and has made five very close friends. Now that she is turning eighteen, Celestia will expect a whole lot more from her but what will wind up being thrown her way will not only affect her significantly, but the lives of her friends as well.
To completely understand this story the following stories must be read or you may find yourself wondering how certain things happened.
-- "An Unlikely Love: The Tale of Two Friendship Students," especially with the alternate ending.
-- "Resetting Her Destiny"
-- "Celestia's Protege"