It was not clear whether the ambulance came from Milton or Balclutha, but its two female officers are thought to have arrived at the scene about 4.30am.
The informant said, after initially entering the property and failing to find the woman, the officers became ''spooked'' for unknown reasons, and left the house to remain in their ambulance.
A second crew from Mosgiel was summoned, but also remained outside the house while a call was put in to police for support at the scene.
The informant said an on-call officer from Balclutha arrived about 5.30am and immediately entered the property, quickly locating the woman in the rear of the house.
No danger to emergency service personnel had been identified at that time.
Although the woman was believed to suffer from several medical conditions, the informant questioned whether more decisive action on the part of paramedics might have prevented her death.
''I believe the fault here lies with the ambulance crew. It's just not good enough,'' the source said.
St John confirmed an incident had occurred, but declined to comment further.
''St John can confirm ambulance officers did attend a callout at a Milton address on the morning of January 15. Given the matter is now before the coroner, we are unable to comment further at this stage,'' rural Otago territory manager James Stewart said.
Balclutha police also declined to comment in detail on the matter, but confirmed the Milton and Balclutha stations were unmanned at the time of the alleged incident, in line with standard operating procedure.
Family members said the woman was a ''much-loved mother, sister and Nanny'', and would be missed by all who knew her.
However, they declined to answer questions about the circumstances leading to her death, ''until a report from the coroner's office is released and inquiries with the police have concluded''.
First published in the Otago Daily Times. Used with permission