I think that Ruth's function as a clone is significant to her characterization. Indeed, she functions as a clone, as one will be harvested for others. Yet, her entire being until the end of her life when she confesses her true motivations to Kathy, is to be a clone of others. She wishes to work in an office, an atmosphere where replication and duplication are part of the Status Quo. She wishes to wear nice clothes, again reflection of a copying mentality. She desires social acceptance and the power of moving from margin to center. Ruth recognizes that this can only be possible, if at all, through duplicating the patterns of powerful individuals. I tend to think that Ishiguro might be making a statement about how our desire to conform and homogenize that which is unique and distinct makes individuals clones in their own right, able to be taken advantage of and "harvested" by the will of those who we wish to emulate. In this light, Ruth's primary purpose is to represent the dangers and destruction of being a literal clone and also being one in spirit. It is here where she is in stark contrast to Kathy, whose distinctive caring nature does not dissipate regardless of her own condition of being. Ruth's function in the novel becomes significant as it shows the fundamental nature of wanting to be part of a group whose intentions are to use people as means to ends as opposed to ends in of themselves.