Is it necessary to make a choice on this question? I think that Lily values both. Lily is in need of love in her life because her mother died, and her father, while he might very well love her, is incapable of showing that, so her life feels like a loveless prison to her. August is a mother figure to her, accustomed to mothering her younger sisters wisely and well. She gives Lily love, and because August knew Lily's mother, it is though her mother has returned to her in a way, through August. Black Mary represents a spiritual love, which Lily was missing in her life. Also, Lily is seeking her freedom, so the statue, who is said to have broken free from her chains, also represents freedom to Lily. Additionally, Black Mary represents a spirituality that is female, and that is something that Lily particularly values because of the loss of her mother.