Against the Rules (Sweet Valley Twins) by Suzanne, Jamie
Sophia Rizzo is a good writer on the school newspaper, she's nice, and Elizabeth likes her. But all the other kids at Sweet Valley Middle School--including Elizabeth's twin sister, Jessica--make fun of Sophia because her family is poor and her brother is always in trouble. Even Elizabeth's parents tell her to stay away from Sophia.
To show Sophia that she's her friend no matter what anybody says, Elizabeth decides to go against strict orders from her parents and throw a secret birthday party for Sophia. But is Elizabeth willing to pay the price if she's caught?