Kelsea Ballerini‘s current single is “heartfirst.” Kelsea shares the story behind the song, “I wrote this song ‘Heartfirst’ with my friends, Karen Fairchild of course, from Little Big Town, and Alysa Vanderheym. And we were all just talking about music that we’re inspired by right now, and wanting to write something upbeat, warm and free-feeling, and just being people…