Sapphire Shores is one of the biggest pony pop stars in Equestria, and a client of Rarity’s. She appears in the episodes “Dog and Pony Show,” and a few seasons later, in “For Whom the Sweetie Belle Toils,” in which she mentions that the dolphin is her lucky animal, as they swim with her in her dreams.
She is sort-of like the Beyonce of the MLP universe.