The Cousin War — Francine Pascal

Elizabeth and Jessica Wakefield are psyched when  their favorite cousin, Robin, comes to visit. They  can't wait for Robin to meet their friends_and  maybe even find a date for the Girls-ask-boys dance  at Sweet Valley Middle School.

When Robin  meets Todd Wilkins, she's certain he's the one for  her. But she's in for a big surprise: Todd already  has a girlfriend Elizabeth ! Will Robin have to  fight her own cousin to win the boy of her dreams?