So sunny that her sharp songwriting can be overshadowed, Kelsea Ballerini nimbly navigated the line separating country and pop in the second half of the 2010s before she decided to ignore borders altogether in the subsequent decade. Ballerini had hit singles right out of the gate, racking up three successive Billboard Country Airplay chart-toppers -- "Love Me Like You Mean It," "Dibs," and Peter Pan" -- between 2014 and 2016, laying the foundation for a career that subtly adapted to shifting trends. Her versatility meant that she didn't stay strictly in a country lane. In 2018...