Hi Mike
In light of the information provided in this thread, and with no satisfactory answer to your question being posted here yet, i thought i might offer the following as a
*possible* lead. My apologies in advance if it leads you astray or if you have already discounted it in your research.

According to the NSW Governments on-line index to deaths:
in 1961 is recorded the death of Charlotte Agnes DEEGAN, Father William, Mother Elizabeth(i see this doesn't line up but meh...). The event was registered in PENRITH district.
I am supposing that this could be a possible transcription error of DEEN in the index.
For what it's worth, this is the only person with the Last Name DEEGAN whose death was registered at PENRITH.
Submitted for your interest.