The anti-mother
In a novel, when a mother reflects the opposite principles of motherhood, that elevates the child to the role of hero or villain; children become more dynamic without the central support of a parent. That is certainly the case for Ruby who is essentially shaped as a character by the chronic and growing suspicion that her mother does not love her at all. Her suspicion grows through life and learning and is eventually confirmed by her mother's decisions, but to what avail? Through the frustration, she learns to support her own self, with allegorical consideration.
The dead father
As a foil to the mother motif, Ruby's relationship to her father is also damaged, however the contrast of this parental foil is life and death; the mother is alive but negligent, and the father is corrupt and dead. The literal effect of this motif is that Ruby's relationship with her mother constitutes the entire dynamic which shapes her self-esteem—there is no father figure to help her stand up against her capricious mother. She is raised to hate him for cheating, but if she treated him with the coldness and hostility she treats Ruby with, perhaps Ruby might have found peace by knowing him. He symbolizes a loss of potential.
The man with mystery
Ruby's mother is a serial monogamist, accepting affection from man after man in exchange for seasons of stability and emotional support. These men are direct evidence to Ruby that her mother is only thinking about herself. When a new boyfriend tells Ruby that she is responsible for a death, the symbolism becomes archetypal. As a symbol for guilt, this friend of the negligent mother becomes a symbol for religious shame which is tied up in Ruby's feelings of insecurity and worthlessness. Now that she feels guilty for murdering her own sister (unfairly to be sure) she must find a way to become peaceful.
The truth of the sister
In reality, it was Gillian who told Ruby and Pearl to walk on the iced over lake. When Pearl fell through, Gillian blames the daughter knowing that she won't have enough wherewithal to defend herself, knowing also that she can get away with it by manipulating Ruby into deep feelings of sorrow and regret. Ruby represses the memory, but the truth of that repressed memory is actually amnesty. She knows now that this parent is abusive emotionally, using the daughter as a scapegoat for the negative consequences the parent is unwilling to accept.
The allegorical ending
It is not hard to decipher the ending of the novel as an allegorical lesson. The ending features a direct, thematic conversation between Ruby (recently escaped from the emotional confusion of her mother's shame and guilt) and her sister (a positive foil for the mother's negative example of womanhood). They discuss the intimate emotions of a child and they agree that they will make oaths to protect children from feelings of internalized guilt and shame. They will also forgive themselves for the confusion their own emotional abuse caused.
