Luna has been redeemed by the elements of harmony, but is finding that salvation is harder to come by. Ponies avoid her, the memories of Nightmare Moon still fresh in their minds. Additionally, after a thousand years of solitude and silence, she’s having trouble adjusting to life in noisy, crowded, living Equestria.
Change never happens easily, and Luna struggles despite the help of her sister and new friends, failing as much as she succeeds.
Perhaps the Moon, her prison for so very long, is truly where Luna belongs after all.