Who is Kate Gulden from One True Thing and what is their importance?

Kate Gulden is a fifty-something year-old housewife and mother of three children: Kate, Jeff, and Brian. Kate falls ill with cancer and does not want her daughter, Ellen, to return home from the city to care for her. When Ellen comes home anyway, the two struggle to create a mother-daughter relationship as they had never had when Ellen was growing up. Throughout Kate's treatment, the two women bond through cooking classes, a book club, and sewing lessons. Kate passes on many unexpected pieces of advice to Ellen who learns that she had underestimated Kate's wisdom her entire life. Kate has always felt inadequate when it comes to her husband's academic achievements, and they way he and Ellen bonded over literature.