Molly Meets Trouble (Whose Real Name Is Jenna) — Megan Atwood

There's a new girl in the third-grade, and for some reason, she brings out the worst in Molly. If only Molly's cross-country pen pal, Olive, were there. But Olive's got her OWN set of troubles with her new gymnastics team. As both girls struggle to make new friends, their dishonest emails and letters to each other threaten their relationship. First-person narratives that alternate point-of-view from chapter to chapter bring the main characters to life.