After matriculating, Sumner moved to London to study and teach English. In 1922 she completed her English Literature studies, receiving a Master of Arts degree from Oxford University. Although she had trained to be a teacher and her father thought art an unstable career, her temperament was that of an artist. Soon after completing her studies she decided to pursue a painting career.
• Berman, E. (1993). Painting in South Africa, Halfway House: Southern Book Publishers.
• Verwey, E. J. (ed) (1995). The New Dictionary of South African Biography Volume 1, Pretoria: HSRC Publishers.