Thank you Wivenhoe.
There are no adoption records - when we wrote to the Supreme Court, they said they were 'lost' - so we have both hospital birth records and adoption records lost........ seems very unfortunate.
However, I do have a copy of some paperwork so she was definitely adopted legally.
Yes, you have the correct Boland family.
We don't know where the baby was during the interim period - I had a bit of a personal theory as this seemed to coincide with the period of Juanita existing on electoral rolls - so I wondered if either she hung around Sydney to be near the baby if it was in an institution, or she and the baby were together during that time and then when she was adopted, she left, or went back to her own name, etc.
This all coincides with the Depression years and also War years - but we have not been able to find any solution there.
Also, although the Nurses Registration records are only now become more available, I am unable to find any nurse Brett or Thompson or Dennan to match - Juanita was listed as a nurse on electoral rolls. I did trawl through the Microfiches at State Records with no luck.
I found a Thank You Nurse Brett notice in Trove for many years later - but it was brief and gave no clues and might not have been anything to do with our person.