Emma Clanton in the series had a romantic interest in Marshal Earp, and in the season in which she appeared, so did hotel owner Nellie Cashman, played by Randy Stuart. In most of the storylines, Earp seemed oblivious to both young women, but kind and respectful toward each. Considering the Gunfight at the O.K. Corral on October 26, 1881, a real Emma Clanton may have viewed Earp as a family obstacle as did the historical brothers Billy and Ike Clanton.

Thurston played the daughter of Newman Haynes Clanton, or Old Man Clanton, and while the real Clanton, an outlaw rancher near Tombstone in the Arizona Territory, had two daughters, neither was named "Emma" but instead Mary Elise and Ester Ann. Lyn Guild (1922–1995) had played the role of Emma in two earlier 1959 episodes of The Life and Legend of Wyatt Earp.

Betty Lou Thurston was born in North Dakota of Irish descent to Harvey E. Thurston and the former Marie O'Loughlin. By 1930, she was residing with her family in Forsyth in Rosebud County in southeastern Montana. By the time she was twelve, she began to work in her father's country repertory company. The Thurstons moved to Billings, Montana, where she was active in the Billings Civic Theater and graduated from Billings High School. In 1942, she moved with her family to Hollywood, where her father began employment with Lockheed Aircraft.

She appeared in eight other films in the 1940s, including the roles of Rosa in the spy thriller, The Conspirators, Siu-Mei in Pearl S. Buck's China Sky, Toni Rosseau in Swamp Fire, Carmelita Mendoza in Jewels of Brandenburg, Narana in Arctic Manhunt, and Watona in Apache Chief.

Thurston was typecast in the role of exotic native girls. She made her motion picture debut in 1944, when Louella Parsons reported that Thurston had been selected over several other actresses by Director Cecil B. De Mille to play the role of the Indonesian girl "Three Martini" in The Story of Dr. Wassell.

Thurston was married three times. By her first husband, David S. Thayer, she had a daughter, Amanda Lycklyn (born February 29, 1948). Five years her senior, Thayer was a commercial pilot and a former lieutenant colonel in the United States Air Force. He played football at the University of Texas at Austin, Texas. The couple married in 1947 in Yuma, Arizona, and divorced two years later. Early in 1954, Thayer crashed a converted bomber owned by the Fullerton Oil Company into a residential district in Burbank, California. Though Thayer escaped with bruises, cuts, and shock, a man alseep in an apartment largely destroyed by flames suffered critical burns. Thayer thereafter became an oil operator and died in his native Houston in 1965 at the age of forty-seven.

In 1949–1950, she was cast in two episodes, "Finders Keepers" and "Masked Deputy," of the early western television series, The Lone Ranger, starring Clayton Moore. In 1952–1953, she performed in six episodes in different roles of another western series, The Adventures of Kit Carson. In 1954, she appeared with Angie Dickinson and Lane Bradford in the episode "Sequoia", on the syndicated Death Valley Days, a western anthology series, then hosted by Stanley Andrews. In 1955–1956, she was cast as Mrs. Cora McGill in "Paper Gunman" and as Annie Brayer in "The Salt War" of another western anthology series, Frontier, which aired on NBC.

Thurston had other guest roles in the 1950s on such series as Sky King, Soldiers of Fortune, The Rough Riders, 26 Men, Behind Closed Doors, Highway Patrol, Westinghouse Desilu Playhouse, and The Man and the Challenge. She was cast twice on the Richard Boone series, Have Gun - Will Travel, and once on CBS's Rawhide as Waneea in the 1959 episode, "Incident of the Power and the Plow".

Thurston also was cast in different roles in four earlier episodes of The Life and Legend of Wyatt Earp before she landed the continuing role as Emma Clanton. In one of those episodes, "Old Jake" (April 9, 1957), Thurston played Mrs. Cafferty, the distraught wife of a soldier who in the episode is killed by a buffalo hunter, Jake Caster (Francis McDonald) because the soldier had participated in the Sand Creek Massacre, in which Caster's Indian wife and son were slaughtered. Ewing Mitchell played a colonel at the then Fort Dodge Army outpost in the segment.

In 1950, Thurston and actor Ross Elliott became engaged, even going so far as to set the date, November 23. That date came and went, however, without incident; less than three weeks later, the wedding was called off. In July 1956, Thurston embarked on her second marriage; this time, to television actor John Russo (1925–2003, known variously as John Duke, Barry Russo, J.D. Russo, and John Duke Russo). By 1959, the two had become estranged, and by February of that year, Thurston was dating actor Jay Douglas (1907-1996). By January 1960, notwithstanding the fact that neither party had as of yet even initiated divorce proceedings, each spouse was clearly otherwise engaged – Russo (aka Duke), with Actress Dolores Michaels; Thurston, with Screenwriter Robert Creighton Williams. Eventually, the divorce was finalized, and, on February 7, 1962, Thurston and Williams were wed. So they would remain until Thurston's death at the age of forty-nine, on New Year's Eve 1969. In the years since her death, the prevailing rumor was that Ms. Thurston committed suicide. However, her daughter, Amanda Thayer, has disputed this, insisting that she witnessed her mother in a Los Angeles hospital after she succumbed to heart failure and spent her last hours in a coma. She was survived by her husband, who died in 1976 at the age of fifty-two, her daughter, and a grandson.

Other than The Life and Legend of Wyatt Earp, her last television role was as Jenny Larson in the episode "Murder Plays it Cool" in the syndicated legal drama series, Lock-Up, starring Macdonald Carey. Thurston never acted again after the role of Smithy's wife in the 1963 Audie Murphy western film, Showdown.