As was mentioned before, apparently all cremations were done in Douglas

I don't have the book which includes the 1967 Yard and Crematorium.
I only have the index to the Rushen Yards and the MI books excluding that one.

From what you already have been told, I'm assuming she was cremated and the ashes placed in Rushen.
The length of the entry in the previously mentioned Burial Register with only the yrs marked would possibly note a small marker appropriate for cremation but I am only guessing.

Someone should either have the 1967 Yard book published by IOMFHS and/or someone could visit the Rushen yard and try to discover the answer.