Describe symbolism in The Last Good Kiss by James Crumley

Fireball is Rosie's aged, feisty bulldog. He adopts Sughrue, or Sughrue adopts him, as a companion. Together they travel the Western states in search of Betty Sue, Trahearne, and the truth. Fireball meets his unfortunate end when he's caught in the gunfire that kills Melinda/Betty Sue in the novel's final chapter. Fireball can be seen as a symbol of Rosie's determination to find her daughter and bring her home alive, a determination that (like the dog) accompanies Sughrue throughout his quest and ends with Melinda/Betty Sue's death.