The duo are accused of kidnapping, torturing and murdering 17-year-old Pairama.
The teen witness - who cannot be named and was given immunity from prosecution by the Deputy Solicitor-General - was at the vacant Housing New Zealand property where Pairama died.
The teen said Pairama, who was also known as Precious, was told to strip naked, before being tied to a chair with rope, and her body burned with a spray can and lighter.
Winter allegedly said: "It's your fault that I got [suppressed] ... how do you wanna die? Karma is a b*tch'. How do you wanna die? You only got 'til three o'clock."
At three o'clock Pairama was to be stabbed if she didn't choose to be hanged, the teen said.
Police investigate at the home in Māngere where 17-year-old Dimetrius Pairama was found. Photo / Doug Sherring
Winter's alleged motive cannot be reported by the Herald for legal reasons.