Away from the flash and topical wit of her biggest hits, Marina Diamandis' songs are as beguiling as modern fairy tales. Her electronic pop is imbued with a touch of pathos, a sprinkle of magic, and theatrical flourishes: The heartbroken-but-still-hopeful “Happy,” for example, is a bruised, beautiful ballad that could easily pass for a gothic-tinged showstopper at a West End musical.