Who is Bea's Mother?

Never named, Bea's mother nonetheless plays an important role in the novel. She disagreed with Bea's decision to take Agnes into the Wilderness. Bea leaves her in the City and proceeds with her plan to join the study. In the years she is gone, Bea's mother develops terminal cancer and dies. The letters Bea discovers from her mother spur her to spontaneously return to the City. Memories of her mother, particularly relating to the time Bea was with both her mother and daughter Agnes, are scattered throughout the novel.