First of all you should perhaps look under Zimbabwe. Apart from that there are very few records on line for the country withe exception of death records, and those only up to 1966. Try looking under Family Search and you will find them but they are not easy to use so be prepared to be patient. I have had a quick look for both Cotter and Berchmans and have not found anything - but that is not to say a more thorough search might not hit the jack-pot. Perhaps it might be better to look for the records of the Order which ran St. Anne's. If she was a member of their Order they would definitely have a record f her demise. Good luck anyway.