Nickname of a much sought after groupie who devoted her life to relieving the loneliness of country and western singers as they travelled on tour across the country. Used, by extension, as a slang term for C & W groupies in general. The eponymous "Butter Queen" was said to use premium non-salted in order to maintain her lubricity. The Rolling Stones sing of being "Down in Texas with the Butter Queen" in "Rip This Joint".
"Man, until we met those Butter Queens in Laramie, I thought that everyone on this tour going to go "brokeback".