Starlight Glimmer is filled with guilt for all the things she did at her old town. She also is wondering why Twilight Sparkle, the Princess of Friendship, is giving her a second chance after all the misery Starlight caused. Twilight and Starlight take the train right after Starlight becomes Twilight's apprentice of friendship.
This takes place during the song, Friends Are Always There For You, in the last episode of Season 5. There is a brief scene where Starlight returns with Twilight to the town Starlight had left at the beginning of the season. I know Starlight returns later in a different episode, but I wanted to write a short little story showing what Starlight might be thinking after her whole ordeal.