Starlight Glimmer is content with running her little village just outside of Equestria's borders. Having built from the ground up with her own four hooves a town where everyone is Equal, Starlight is satisfied. Ponies wander in and they decide to stay. There's no reason for her to return to her homeland.

Then Tirek defeats Princess Twilight Sparkle, and an undercover changeling tells Starlight Glimmer she's the last hope to save Equestria from the mad centaur.