The Proteas chose to bat after winning the toss and got off to a great start with a 78-run partnership from the opening pair before Sune Luus was dismissed for 37 off 24 balls.
Every batter chipped in but the stars of the show were Faye Tunnicliffe's 51 off 41 balls to open the innings and Dane van Niekerk, who dominated the Irish bowlers on her way to a brisk 41 from just 19 balls for a strike rate of over 215.
The combined effort saw South Africa post an imposing 201/5 from their 20 overs, putting themselves in a strong position to sweep the series.
All of Ireland's bowlers took a bit of tap. Still, Orla Prendergast held her own with figures of 1/29 from her four overs. At the same time, Aimee Maguire picked up three wickets but was expensive in conceding 43 runs.
South Africa's bowlers kept things tight even though they struggled to pick up wickets as they restricted Ireland to 136/3 from their 20 overs to secure an emphatic 65-run win to take the series 2-0.
Chloe Tryon was the pick of the bunch, returning figures of 2/24 from her four overs.
Former Bafana Bafana striker Shaun Bartlett believes South Africa may finally have found a player capable of threatening the national team's long-standing goal-scoring records.
South Africa produced a ruthless all-round display to beat India by 51 runs in the second T20I of the five-match series at New Chandigarh on Thursday, taking firm control of the tour.
e South African women's final match of the series against Ireland was abandoned due to bad weather without a single bowl being delivered at Willowmoore Park on Wednesday.
Hardik Pandya struck forceful half-century and then took a wicket as India crushed the Proteas by 101 runs in the first of five T20Is played in Cuttack on Tuesday.
