Laura Wolvaardt, Tazmin Brits and Marizanne Kapp all fell just short of half-centuries on Wednesday as South Africa made 5-166 after electing to bat.
In response, Scotland never recovered after they slipped to 3-34 in the powerplay, eventually succumbing to 86 all out after 17.5 overs.
Following defeats to Bangladesh and West Indies, the result means the end of Scotland's hopes while South Africa boosted their qualification hopes by going top of group B and improving their net run-rate.
South Africa openers Wolvaardt (40) and Britz put on 64 before Wolvaardt played Katherine Fraser into the hands of Olivia Bell in the eighth over.
Anneke Bosch fell for 11 but Scotland had to wait till the 15th over before opener Brits was removed on 43 by Bell.
Kapp's 43 off just 24 balls threatened to propel South Africa out of sight but skipper Kathryn Bryce dismissed the dangerous allrounder.
Sune Luus hit a couple of late boundaries to ensure a daunting target and Scotland's chase was soon in tatters as Sarah Bryce, Saskia Horley and Kathryn Bryce all fell for single-figure scores inside the powerplay.
Ailsa Lister was bowled by Nonkululeko Mlaba for 12, sparking a middle-order collapse that left them 8-67.
Fraser provided some resistance by top-scoring with 14 from 21 deliveries but Scotland fell well short.
Scotland will face England in their final group game on Sunday.
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