Why do you think the author referred to the main character as the girl without using her name until the second chapter

In the first chapter, the author utiliizes Chapter One to set up the main premise of the story and establish its main character. At this point, her name isn't important, as we are meant to see the situation in its entirety. Lisa has been thrust from her old life to her new one..... she's alone with her brother, acting against her own moralistic instincts in order to survive.