There's no sign of a deceased estate file for Rebecca Fenn on NAAIRS. This doesn't necessarily mean she didn't die in SA as not everyone who did so had an estate file lodged with the Master of Supreme Court. Naturally, there would be no will available if no estate file exists. I did find the reference to Taylor enquiring into Rebecca's whereabouts in 1902. You then mention that she was on a passenger list to England in 1934 ? If you haven't found her subsequently on a ship returning to SA, she may have remained in England and died there. Have you checked UK GRO deaths for relevant years?
Mole