To me, this song is about a girl who was in a relationship, but committed suicide (hence the angel), and wants to be the guardian angel of whoever she was with, saying that she'll always be watching over him (shown throughout the song), and the whole "Our love never dies, this love never dies" shows that she'll always love him, and he'll always love her, and that the other person couldn't be with somebody other than the girl.
To me, this song is about a girl who was in a relationship, but committed suicide (hence the angel), and wants to be the guardian angel of whoever she was with, saying that she'll always be watching over him (shown throughout the song), and the whole "Our love never dies, this love never dies" shows that she'll always love him, and he'll always love her, and that the other person couldn't be with somebody other than the girl.