White Ferns captain Melie Kerr was unstoppable on her way to crunching her century off 51 balls.
She finished with a career-best T20 knock of 105 — which included 20 boundaries — and became the first player, man or woman, to score more than 30 runs in 11 consecutive T20 innings.
Kerr backed it up with the ball, taking two for six to secure the White Ferns a 92-run win. wrapping up the series 4-1.
The White Ferns batted first and Izzy Gaze perished lbw in the second over.
Kerr, who was dropped on her opening ball, drilled consecutive boundaries to guide the home side to their half-century.
South African seamer Tumi Sekhukhune soon put a stop to it.
Georgia Plimmer (27) holed out and veteran Sophie Devine was caught and bowled for a golden duck.
That put the White Ferns 54 for three.
Kerr crunched another through the covers and brought up her half-century off 34 balls.
Halliday went big and was removed for 26 and Maddy Green was trapped lbw for six, but there was no stopping the New Zealand captain.
Kerr punished anything slightly wayward from the South Africans, and having already swatted 14 fours, she unleashed with a big six.
She followed up with consecutive fours to bring up her century — and went for another when she was finally removed for 105.
Her sister, Jess, smacked a maximum for the White Ferns to finish 194 for six.
In reply, Lea Tahuhu struck with her first delivery, removing Chloe Tyron.
Tahuhu picked up her second when Anneke Bosch (9) holed out and South African captain Laura Wolvaardt (nine) was caught behind, putting her side 40 for four.
Melie Kerr removed de Klerk and Annerie Dercksen and Devine bowled Karabo Meso for a golden duck as the White Ferns put their foot down.
South Africa crumbled to finish 102 for nine.
In the men’s game, South Africa, batting first, posted a commanding 187 for four, Connor Esterhuizen top scoring with 75 off just 33 deliveries.
In reply, the Black Caps lost wickets at regular intervals and could not sustain the required run rate, falling 34 runs short for the loss of nine wickets.
