In here Twilight told her the story about her having troubles and doubts in light of her coronation, she told Luster that she too during that time feared that her new duty as the new ruler of Equestria will make her drifted apart to her friends, making their friendship fade, but after some numerous obstacles they got along the way followed by a coronation ceremony gone wrong, she realized that she have to make their friendship worked out despite of them living in different places. Twilight decreed to create the “Council of Friendship”, a simple get together every once a moon, that way she and her friends will still get in touch and rule Equestria together.
Luster, having heard and realized the importance of friendship, expressed that she is unsure on to where should she will going to start on making friends and learning more the value of friendship. Because of it, Twilight decided to send Luster to the School of Friendship where she can study, and most importantly, for her to take the small steps of learning the value of friendship.
Since Luster Dawn was introduced at the very last episode, her fate afterwards is sadly unknown and will remain a mystery to all of us. But whatever that is, we’re hoping that she will indeed achieve her dreams just like her favorite teacher and ruler of Equestria.
Based on “The Last Problem” MLP Season 9 epilogue episode and series finale.