"We should have been looking after her.
"It's so important that neighbours look after each other."
People should have known something was wrong, she said.
"Police were there when we got home about 8.30pm ... a neighbour said they had just found her body and she'd been there for three weeks."
The neighbour said there were too many old people who were left by themselves.
Housing New Zealand regional manager Denise Fink said staff were looking into the situation and were in contact with the woman's family and police.
"Generally speaking, we inspect properties twice yearly.
"We don't have a formal policy for instances where tenants have not been heard from for some time, but do rely on neighbours, friends and family to alert us if they are concerned," she said.
A police spokesman confirmed that the woman's death was from natural causes and not considered suspicious.
- Additional reporting: Anna Leask