Bitter Rivals is the 29th book in the Sweet Valley High Book series. This book introduces Amy Sutton, who had made her debut in the Sweet Valley Twins book series, as Elizabeth's childhood best friend, who would become one of Jessica Wakefield's friends.
Elizabeth is clearly excited, because she had received news that her former best friend, Amy Sutton, was returning to Sweet Valley from Connecticut, where she had moved after Junior High. Amy and Elizabeth had been good friends since childhood, (their adventures had been shown in the Sweet Valley Kids and Sweet Valley Twins book series) and had a lot in common. Elizabeth hoped that Amy and her current best friend, Enid Rollins would also get along.
However, all the years of being apart would cause a world of difference. Amy was not the same shy tomboy that Elizabeth had known when they were younger. When she returned, Amy was more fashion conscious, and more than a bit boy-crazy. She also clearly resented Enid Rollins, who she thought was stealing Liz from her.
When a young man named Chris, who was Lila Fowler's cousin, came to town, Lila wanted him to meet Amy, whom she thought was more appropriate for him, but Chris could not stand her, and preferred Enid's company, which angered both girls. Amy threatened Enid for taking both Liz and Chris from her.
Meanwhile, Enid told Elizabeth what Amy had done, and also that Chris still wanted to go out with her. Amy then became one of Jessica's best friends, which somewhat pushed Cara Walker aside, although she was still friends with them, and she became one of Elizabeth's friends.