Who is Mrs. Chilman in Bridge of Clay?

Mrs. Chilman is the boy's elderly neighbor.
Matthew explains that sometimes the phone would ring and one of the five brothers would run next door to help out Mrs. Chilman. The example he gives is that she couldn't get a new bottle of tomato sauce open. Once they were back, life would go on as it had before she called.
In the past, he says that when Penny was giving birth to Clay, the older boys—including Matthew—were left with Mrs. Chilman. During the novel, Mrs. Chilman comes over to help treat one of the boys when he's injured. Henry later thanks her and makes her smile.
Near the end, Matthew explains that Mrs. Chilman never judged the way they lived. Even when their parents were gone, she just let them carry on. She'd bring over soup and ask for help, and that was that. She loves to read. It's clear that she has a lot of affection for the Dunbar brothers.
At the end, Matthew mentions that she died at some point after the main events of the book.