It's Ouma Shu's love for her that gives her a place in the viewer's attention and affection. His devotion, and hers too, and how she sacrificed herelf up to simply save him. I think it's quite obvious Yuzuriha Inori is neither clone nor human. She is a replica, a created body that would be compatable with the consciousnes of Mana and was never meant to have a consciousness of her own. This is why she calls Tsutsugumi Gai her saviour, he pulled her from the hold, forcing the body to gain a soul.