I think it's a little deeper than that. She says "You know I am beyond reach forever." The mere fact that the dead girl is singing shows this song has some sort of afterlife theme. One of them must have done something so that they can't be reunited after he dies, most likely she killed herself, because she says she feels the same tormenting pain and she has paid enough, giving her character a feel of depression.
I think it's a little deeper than that. She says "You know I am beyond reach forever." The mere fact that the dead girl is singing shows this song has some sort of afterlife theme. One of them must have done something so that they can't be reunited after he dies, most likely she killed herself, because she says she feels the same tormenting pain and she has paid enough, giving her character a feel of depression.