I am obsessed with Kenyan colonial history and I am currently reading a book titled Endless Horizons by Michael Prettejon and he talks of his wife Gillian Rutherfurd. I wonder if this is who you are referring to. The Prettejohn’s are still prominent in Kenya and you can look them up on social media or atleast their children and grandchildren with that last name. You can also contact ‘old African magazine’ and they do a great job compiling stories of colonial Kenya. Hope this helped !!!