News Once-beefing Nashville stars performed their new song 'Horses and Divorces' Kacey Musgraves, Shane McAnally, Miranda Lambert and Brandy Clark celebrate their chart-topping single "Mama's Broken Heart" on Sept. 11, 2013, in Nashville (photo: Rick Diamond / Getty Images for BMI). Kacey Musgraves and Miranda Lambert officially buried their decade-plus-old beef last night (May 5) at the former’s show in New Braunfels, Tx., when they performed their duet “Horses and Divorces” from Musgraves’ new album, Middle of Nowhere . See fan-shot footage below. As the story goes, Musgraves long harbored resentment that a song she wrote and intended for her own debut album, “Mama’s Broken Heart,” was instead recorded by Lambert and became a huge hit. Musgraves recently admitted to Variety that she and Lambert had “grass-fed, grade-A” beef  between them largely ever since, but that it felt like time to flip the script while working on Middle of Nowhere .…