On Monday, the court heard the motive for the double murder was to get a share of the inheritance.
State prosecutor Rea Mima said they also planned to kill the parents so the boyfriend, Mathew Naidoo, could stay on in the house in Thames Avenue, Westville, Durban.
According to statements handed to the court on Monday, Nicolette said Naidoo had told them he was the "third son of God... that he had an angel and demon in him and that he was a vessel of God through which angel and demons could speak.
"We believed Naidoo hook, line and sinker," Nicolette said.
The victims, Magdelena, 52, a teacher, Johannes Lotter, 53, a businessman, had been unhappy about Naidoo living in the house.
Later evidence in court on Monday was that Magdelena had kicked him out. All three accused pleaded not guilty to the July 19 2008 double murders.
Magdelena died from "multiple penetrating injuries to the left lung", while her husband died from strangulation.