In 1906 she married William Scoresby Routledge. The couple went to live among the Kikuyu people of what was then British East Africa, and in 1910 jointly published a book of their research entitled With A Prehistoric People.
In 1910 the Routledges decided to organize their own expedition to Easter Island/Rapa Nui.
Scoresby and Katherine separated in Sydney, Australia, in 1923, although for several years they periodically lived together in both London and "The Ewers", their home in the countryside of Hampshire. They finally parted company in 1928 when Katherine’s encroaching mental illness lead to her being institutionalised. This brought to a sad end an extremely productive collaboration that provided invaluable research and preservation of the anthropology and ethnography of Kenya and Easter Island.
Scoresby preserved as much of Katherine’s work as could be found by donating it to both the British Museum and the Pitt Rivers Museum in Oxford