How does Doreen die in the novel, The Queen of Dirt Island?

One night, when Doreen fails to bring Pearl home on time, Saoirse, Eileen, and Nana rush to Chris's farm. With Chris's help, they find Doreen and Pearl. Doreen has taken the baby to a nearby pool. The pool is hidden in the grasses and is rumored to reach to the center of the Earth. Because of the stories surrounding the pool, the family is terrified that Doreen will throw herself and the baby into it. They ultimately get Pearl to safety, but Doreen casts herself into the pool where she dies.