Soon after play resumed, South Africa made early inroads in just the second over. Nadine de Klerk struck first, dismissing Kavisha Dilhari on the final ball of her over as the batter was caught out. Off the very next ball, Mlaba removed Harshitha Samarawickrama, who miscued her shot and was caught soon after.
After the dismissals of Dilhari and Samarawickrama, Gunarathne anchored the innings and took charge. However, mounting pressure from the Proteas saw the hosts lose momentum late in the innings with three wickets falling in the final over.
Nilakshika de Silva was caught in the deep and later, Anushka Sanjeewani was run out while trying to complete a second run. Mlaba then capped off an excellent spell by removing Gunarathne, who edged one to the keeper while attempting a big shot.
The win for Proteas puts them in good stead ahead of their sixth match of the league stage against Pakistan on October 21 at the same venue. Meanwhile, Sri Lanka will face off against Bangladesh in Navi Mumbai on October 20.