South Africa took the lead inside a minute when Zenay Jordaan scored.
Mathrin Simmers made it 10-0 just two minutes later to put South Africa in firm control.
But the Palais hit back immediately through Fatima Rama. A successful conversion from Joana Lagona put the score at 10-7.
A try to South Africa before the half-time whistle gave them some breathing space with a 17-7 lead.
Tries to Nadine Roos and Phumeza Gadu in the second half sealed the win for South Africa advancing them onto the next stage of the tournament.