I'm awaiting the Death Certificate from the IoM Registry, whether this will give me any information that will help, I don't know. Perhaps the person reporting the death.
It does seem a long shot that someone who died in Morpeth in 1938 was then buried on the Island in 1951. I assume the Burial Register at Lezayre is exactly what it says it is, a register of burial rather than register of death, but she was registered on 13 October 1951.
Thanks for your interest.