Marshmallow Skye by Cathy Cassidy

Second Hand 

SKYE and SUMMER TANBERRY are identical twins, and Skye loves her sister Summer more than anyone else in the world. They do everything together, but lately Skye's been feeling like second-best - it's the story of her life. And when her friend Alfie confesses he's fallen not for her, but for Summer, it hurts.

Skye wants to be her own person, but with an effortlessly cool twin, how can she? Will Skye ever step out of Summer's shadow and find her own chance to shine?