In Geraldine Brooks' Year of Wonders, personally, I see the relationship between Elinor and Anna as a reflection of how the town of Eyam changes as it faces the many effects of the plague. New relationships are formed—enemies become allies and unlikely friendships develop. "Wonders" in the title speaks to the positive changes that Anna (the main character) witnesses during a time of devastation.
Anna is the housekeeper at the rectory, the home of Elinor and Michael Mompellion—he is the town's preacher (minister). It would seem that the preacher's wife and her housekeeper would have nothing in common. Anna is one of the "common" folk, while Elinor would be considered of a higher station. In fact, while Elinor first may attempt to "better" Anna—maybe perceiving her as an inferior—Anna does not mind this "education;" she welcomes the knowledge. Elinor begins to earnestly teach Anna to meet Anna's "hunger" for information. Anna even learns to read.
"Good morning, Anna," [Mrs. Mompellion] said as she saw me. "Did you know that the tea made of this unassuming little flower serves to cool a fever? As a mother you'd do well to add some herb lore to your store of knowledge..."
This incident foreshadows not just the need of herb lore, but the relationship that Anna and Elinor will develop as healers.
The arrival of the plague demonstrates the ability or inability of people in the town to rise above their differences to aid others.
The crisis brings out the best and worst in the community. Some behave with great generosity and altruism, some with malice and greed.
When Anna's youngest son dies and her stepmother criticizes her for the death based on superstitions, it is Elinor who comforts Anna, reading to her from the Bible—about how Jesus loved and valued all children.
As the story progresses, disasters that occur because of the plague and the ensuing madness of the villagers cause unexpected hardships: the murder of the Gowdies (the town's healers) creates a lack of medical help and midwifery. Anna and Elinor decide to try their best to provide help in these areas and they experience some success. Their bond of friendship grows. They help young Merry Wickford who may lose the family's mine (after her family members all die) to collect lead; this saves the mine, but also allows the Anna and Elinor to join the Miner's Tavern—not just a meeting place, but the town's judicial system, of which Anna and Elinor are not a part.
The effort the women engage in to help others allows them to form a deep and meaningful friendship. This is similar to many things that occur in the town of any value. Those who see to the needs of others find they are many times rewarded with a fuller life and a community that, in many cases, is much more tightly knit.
While the women's friendship is a metaphor for the book's theme of coming together during adversity regardless of differences one may have with another, it is also the heart of the novel. After Elinor is killed, Anna adopts a baby she saves from death, and traveling to a distant shore, gives birth to a baby—father by Elinor's husband (Michael) after Elinor's death. The child is named Elinor, honoring their friendship. Anna's ability in her new life to become someone she never would have recognized years before is in large part due to the connection she made with Elinor. And another of the "wonders" she witnesses.