De Sielvie completed her senior school certificate in 1968 in Sri Lanka, and subsequently worked as a stenographer in an advertising agency in Colombo before studying Journalism at the Ceylon College of Journalism. She was awarded a Diploma in Journalism in 1970 and in that same year married Conrad de Sielvie, an architechtural draftsman, before migrating to Australia with her husband in 1972, due to the political unrest in Sri Lanka at the time. She has two children.
De Sielvie has written short stories, poems and articles which have won prizes in local newspapers and magazines, some of which are also included in Writers World anthologies. Since 1996 she has lived in Frankston, Melbourne, where she pursues her hobbies of painting, reading, music and writing, and she is a member of the Society of Women Writers in Victoria and the Peninsula Arts Society. De Sielvie studied at the Melbourne Institute of Art and was awarded a Diploma in Commercial Art in 1982. She worked as a public servant for many years and is currently writing an autobiography.