The New Girl (Sweet Valley Twins)
Identical twins Elizabeth and Jessica Wakefield don't always  agree on things--until Brooke Dennis arrives at Sweet Valley. Both  twins agree that she's horrible. She snaps at everyone who tries to be  nice to her and she's constantly saying mean things to people.To  get even with Brooke, the twins invent a third lookalike sister whom  they call Jennifer. Pretty soon all of Sweet Valley Middle School is in  on the plan. But then Elizabeth discovers the real reason why Brooke is  so mean. Suddenly, the plan to get revenge doesn't seem like such a  good idea. Can Elizabeth stop her classmates from playing the ultimate  joke before Brooke's heart gets broken?