How does the author use foreshadowing in What Was She Thinking? Notes on a Scandal?

In the novel's foreword, Sheba, the protagonist, and Barbara, the narrator, are introduced to the reader. The tone of the foreword is confidential, as well as decidedly judgmental. In order to gain the reader's trust, Barbara shares a few of Sheba's secrets. Barbara also provides a few small details about herself. She foreshadows later events in the novel by dismissively saying she has a minor role in the events of the scandal. Barbara also creates the perception that Sheba is a fragile and weak-minded person. While Barbara sheds doubts on Sheba's reliability, the reader will learn that Barbara herself is a less than reliable narrator.