Rachel is one of the three primary supporting characters in the novel. Rachel, like Jacob, has been blind since birth. Unlike Jacob, this has seemingly not left her with any of his unique abilities. Part of the plot for all of the books is that the primary characters are, in some fashion, chosen. That does not mean that Rachel’s role in this is at all minor.
Rachel becomes Jacob’s anchor to our reality brought about by the love that develops between them. As is seen late in the novel, this in itself brings about what can only be called a miracle.
In an earlier blog post, I mentioned that Aura is filled with allegory and symbolism, Rachel is one of these symbols. She represents a part of humanity that exists in all of us, the part that struggles to see and is awed by the wonder of a world that few ever get to experience.