It is indeed the same Amy. There will definitely be, band harem is still being worked on.As of right now there's two different band harem ending, one where you marry Anna and Kleio, and another where you marry all three so I don't see why a third ending wouldn't be possible, I mean they do mention that the girl that left the band after sleeping with Anna was called Amy so going off context clues (A girl who's into women, can play guitar, left a band, ect) would seem the Amy we meet is the same Amy that left the Deathless Harpies I wonder if this mean Amy will be rejoining the band?