In an update on Monday, Detective Senior Sergeant Tim Leitch said an arrest was made on Monday morning.
“A 52-year-old woman was taken into custody and has been charged with murder in relation to Helen’s death,” Leitch said in statement.
“This is a significant development in the investigation and our thoughts are with Helen’s family at this time.”
The 52-year-old is due to appear in Wellington District Court on Tuesday.
Last week, a police spokesperson said it’s believed some items were dumped at a Porirua landfill after Gregory’s death, and specialist search teams were involved in seeking for them.
On Monday, Det Snr Sgt Leitch said the search was completed on Saturday and a search is ongoing at the woman’s address.
“Police would like to acknowledge the response and support of the community during the investigation and urge anyone who may have information and has not yet contacted Police to do so,” he said.
“As this matter is now before the court, we are limited in making further comment.”