Who is Kills-close-to-the-lake from Fools Crow and what is their importance?

Kills-close-to-the-lake is the third of Rides-at-the-doors three wives, she is a shy, slim girl who is one year younger than her stepson White Man's Dog and a year older than his brother Running Fisher. White Man's Dog finds her attractive and struggles with mixed feelings toward her has he finds her desirable but logically knows she is his "near mother." Rides-at-the-door brought her into his lodge as an act of kindness, but she is not happy. Due to the sexual tension between her and White Man's Dog, he does his best to avoid her. When White Man's Dog marries and moves out, Kills-close-to-the-lake becomes Running Fisher's secret lover. When they are found out by Rides-at-the-door's middle wife Striped Face, Kills-close-to-the-lake is banished.