Who is Rhonda Pommeroy from Stern Men and what is their importance?

The mother of the large Pommeroy family that lives next door to protagonist Ruth Thomas, Rhonda bears seven sons in six years: Webster, Conway, John, Fagan, Timothy, Chester, and Robin. Her husband calls her Wanda, mimicking their son Robin's speech impediment, and the nickname spreads across the island. Most of the time, she is simply called Mrs. Pommeroy. Rhonda is not yet sixteen when she marries her cousin Ira, whom she adores above everything in life and whom she annoys with little gestures like tweaking his nipples and playing "Feet on you" when drunk. Rhonda drinks daily, even when pregnant, which some claim accounts her boys' inability to read.