Playing their first competitive game for their country in close to 11 months, the South Africans made 196 all out after winning the toss and batting first. England then chased down a revised victory target of 150, twice adjusted after rain delays, with 39 balls to spare.
Opener Chetty was the cornerstone of the hosts' innings as she comfortably past her previous best score of 76* against Bangladesh at Centurion back in 2013. Fellow opener Laura Wolfvaardt, making her debut at the tender age of 16, put on 26 for the first wicket before she fell for 5. The teenager was one of four wickets for Player of the Match Anya Shrubsole, who claimed 4/29.
Captain Mignon Du Preez (38) and Chetty then provided the hosts with a splendid platform thanks to their 93-run, second wicket stand. The skipper eventually fell with the total on 119 - Shrubsole claiming wickets off successive deliveries to jolt South Africa's progress. Her other wicket was Marizanne Kapp (0) and the loss of those two key wickets knocked the home side's confidence.
Although a tiring Chetty, who suffered cramp along the way, kept going, her 122-ball innings (nine fours), eventually ended when she edged Heather Knight behind to Sarah Taylor leaving the Proteas women all out with four balls to spare. Kapp (1/26) claimed the wicket of Lauren Winfield (10) with the total on 29, but a quick-fire 34 off 27 balls (6 fours) by Amy Jones provided the tourists with impetus. They were 63/2 in 13.1 overs at the first rain delay and kept scoring well after it when the target was revised to 194 from 48 overs.
England captain Charlotte Edwards (33) was bowled by Marcia Letsoalo (1/20) after the delay, but Taylor's unbeaten 41 and Knight (26) took the visitors home following a second delay that lasted just under an hour. The second match of the series takes place at SuperSport Park in Centurion on Friday.