Elizabeth's Secret Diary, Volume III — Francine Pascal

Elizabeth Wakefield has a confession to make. She's met a guy--an intelligent, caring, and unbelievably handsome guy. But it's not Todd Wilkins, her longtime boyfriend, whom she loves more than anybody. It's Sam. Elizabeth wouldn't even need to change her initials. Mrs. Elizabeth Woodruff. She's fallen hard. But no one can know about Elizabeth and Sam, especially not Jessica. She could never keep a secret this big. And if Todd ever finds out, it'll break his heart.