I have recently seen the noun mem-sahib, used to refer a white foreign woman living in India, in two different books. The books are Indian Passion and Nowhere in Africa.
I have not found any information about the use of mem-sahib in other countries, but in the latest book, I have seen this word many times even though the story happens in Kenya. If mem-sahib comes from a mix between English plus Hindi and Urdu, why did people use the word in Kenya if they had their own words like bwana to refer to a boss, for example? Did they really use it, and was it common in other countries?