One was calling out "Mama, Mama" as the soil was shoveled over his head, said Marabe, who works for a volunteer organisation called Igat Hope, Pidgin English for I've Got Hope.
"One of them was my cousin, who was buried alive," she told reporters.
"I said, 'Why are they doing that?' And they said, 'If we let them live, stay in the same house, eat together and use or share utensils, we will contract the disease and we too might die.'"
Marabe appealed to the government and aid agencies to ensure the HIV/AIDS awareness programme carried out in cities and towns was extended to the rural areas, where ignorance about the disease is widespread.
Women accused of being witches have been tortured and murdered by mobs holding them responsible for the apparently inexplicable deaths of young people stricken by the epidemic, officials and researchers say.
A recent United Nations report said PNG was facing an AIDS catastrophe, accounting for 90 percent of HIV infections in the Oceania region.
HIV diagnoses had risen by around 30 percent a year since 1997, leaving an estimated 60,000 people living with the disease in 2005.