The police in Waikato say they received three emergency calls about a woman before her neighbour was killed at a house in Frankton on Tuesday.
A full investigation is underway amid claims the woman had earlier fled a mental health facility in Hamilton. The Waikato District Health Board is not commenting on the claims.
The 40-year-old appeared in the Hamilton District Court on Wednesday charged with murdering her neighbour in her Blackburn Street home. She has been remanded in custody for a psychiatric report.
District commander Superintendent Allan Boreham says the police responded twice to calls that the woman had threatened her neighbour, and found the body of the dead woman, 53-year-old Diane Elizabeth White, on the second call-out.
Hamilton police are working with Interpol to contact the dead woman's family. Formal identification has been completed, and efforts are underway to locate a family member who is believed to be in Australia.
A scene examination was continuing at the homes of both the arrested woman and the victim, and police are still interviewing witnesses.