Bertha Blount was born on 10 October 1882 at Macomb, Illinois. She received her early education at Park College Highschool in Phoenix, Arizona, and attained her B.A. degree at the University of Michigan in 1907. On 6 July 1908, she was appointed by the Presbyterian Church USA mission board to Siam, sailing on 16 September 1908.

Upon arrival in Bangkok, Bertha served at the Wang Lang School and then the Wattana Academy. In 1914, during her first furlough, she resigned as a missionary to take on the task of caring for her mother. In June 1918, she was reappointed and returned to Thailand with her mother. After Edna Cole retired, Bertha became the principal of Wattana Academy and held that position until she married Dr. George McFarland on 25 February 1925, becoming his second wife. After she married Dr. McFarland, she became an affiliate member of the Siam Mission.

Along with her noteworthy accomplishments in serving at both Wang Lang school and Wattana Academy, Bertha contributed significantly to the cause of missions in Thailand. She served as Secretary of the National Christian Council, which led to the formation of the Church of Christ in Thailand. As a faithful member of the Siam Mission's Survey Team, Bertha worked alongside Rev. Paul Eakin and Pastor Pluang Suddhikham. As wife to Dr. McFarland, she assisted with many of his business ventures, including their typewriter store. 

When World War II arrived in December 1941, she and her husband were not interned in the prisoner camp. Dr. McFarland's connections with the Thai government allowed their being restricted to their home. On 4 May 1942, Dr. McFarland passed away at his home. She later joined other Americans in the prisoner exchange between Japan and the U.S., and she arrived back in New York on the exchange ship M.S. Gripshold on 25 August 1942.

Around 1950-51, Bertha returned to conclude some of the businesses belonging to her and her late husband. When she returned to the U.S., she was already ill and died on 27 January 1952.

Bertha was an accomplished writer, assisting her husband in the editing and writing of the Historical Sketch of Protestant Missions in Siam. After her husband's death, she wrote the biographical works of Our Garden was So Fair and McFarland of Siam: The Life of George Bradley McFarland, M.D., D.D.S. Afterwards Phra Ach Vidyagama.