Explain Grace's remark that she is the mother of Cain and Abel in the book The Westing Game.

Grace so obviously favors Angela over her other daughter, Turtle, that the parallel to the Biblical story of Cain and Abel is less far-fetched than it may seem.  Though there are a few differences between Cain and Abel and Angela and Turtle (such as the favored child, Angela, is the eldest, which is the reverse of the Bible story), and certainly Turtle, the unfavored daughter, doesn't kill her sibling as Cain does to Abel.  This is just Grace's tactless way of showing the difference between her two daughters.  It is a shallow, rather cruel comparison, and is actually inaccurate.  Angela may be the favored child, but her favored status is only created by a front that Angela puts up.  Angela has been guided by Grace so entirely that Grace is trying to realize her own frustrated dreams through Angela's life.  Cain really was a spiteful and murderous man, who killed his brother out of jealousy.  Turtle, who is somewhat jealous of her sister, does nothing unkind to her, and, in the end, helps Angela to throw off the front of the meek and "perfect" daughter that Grace had wanted, and let Angela become more fully herself.  Grace's remark is indicative of her own tendency to see and value only the surface and appearance of things, rather than the reality underneath -- even in the characters of her own daughters.