In 1934, after winning a fellowship to study in Swaziland, Kuper befriended King Sobhuza II who, together with Malinowski, helped to settle her into place at the Royal village of Lobamba, where she would pursue her research. Her publications on Swazi culture would include the two-part dissertation, An African Aristocracy: Rank among the Swazi (1947) and The Uniform of Colour: a Study of White–Black Relationships in Swaziland (1947), and The Swazi: a South African Kingdom (1963).
Some years later, in Durban, Kuper became a founder member of the Liberal Party in Natal, as well as authoring Indian People in Natal (1960).
In 1961 Kuper moved to Los Angeles, where she took up a teaching post at UCLA. In 1969 she won a Guggenheim fellowship, and in 1978 published an extensive, official biography of Sobhuza II, King Sobhuza II, Ngwenyama and King of Swaziland.