In Some Other Life by Jessica Brody

Kennedy Rhodes turns down an acceptance to an elite private school, instead choosing to stay at her high school and jump at the opportunity to date the boy of her dreams. Three years later, Kennedy walks in on that same boyfriend cheating with her best friend—and wishes she had made a different choice. But when Kennedy hits her head and wakes up in the version of her life where she chose to attend the private school, she finds that maybe it’s not as perfect of a world as she once thought.