Who is Bonnie Lisbon from The Virgin Suicides and what is their importance?

Bonnie Lisbon is a blonde fifteen-year-old girl who's noticeably taller than her sisters are. She has light skin, and she's quiet and very pious. Beside Lux and Mary, Bonnie is the only girl that can be observed regularly by the boys after Mrs. Lisbon's imposed shutdown on the house. She often appears on the porch reciting the rosary, as one of the rare signs that something is still alive in the Lisbon house. On homecoming night, she is Joe Hill Conley's date. On that particular night, she appears friendly and outgoing. The body of Bonnie is the first discovered by the narrators on the night of the failed rescue. On June 15, the same day that Therese and Lux die, she commits suicide by hanging from a beam located in the basement of the house.