Sent into bat, West Indies women made 137 for five and then bowled out the hosts for 106 in 18.1 overs.
WesT Indies score was built around four batters -- captain Stafanie Taylor (47), Deandra Dottin (35), Hayley Matthews (27) and Merissa Aguilleira (21).
For India, medium pacer Shikha Pandey picked up two wickets giving away 29 runs.
Chasing the target, India never recovered from an early batting colapse and their innings eventually folded with the loss of six wickets for just 33 runs.
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Other Indians to score double digit scores are Deepti Sharma (24) and Meghna Singh (17).
For West Indies, Anisa Mohammed (3/23) and Deandra Dottin (3/24) took three wickets each,
But India would also take confidence from the fact that
both pace and spin did the trick in defending the target. New-ball bowler Shikha Pandey took four wickets while left-arm spinner Ekta Bisht grabbed three wickets in that match.
"Our bowling looks good, especially the spin attack. But in batting our concern is the opening partnership, especially in the first 10 overs -- whether we bat or field, we need a good start from the openers...It is also imperative that the middle-order batters be among the runs," Mithali said.
For South Africa, 17-year-old opener Laura Wolvaardt and Chloe Tryon have come up with crucial performances while the leg-spin pair of captain Dane van Niekerk and Sune Luus have had consistent success. Pace bowlers Shabnim Ismail and Marizanne Kapp too have been effective.
But South Africa's challenge will be against India spinners Bisht, Rajeshwari Gayakwad, Poonam Yadav and Deepti Sharma.
India: Mithali Raj (captain), Ekta Bisht, Rajeshwari Gayakwad, Mansi Joshi, Harmanpreet Kaur, MD Thirush Kamini, Veda Krishnamurthy, Mona Meshram, Shikha Pandey, Deepti Sharma, Sushma Verma, Devika Vaidya, Poonam Yadav, Soni Yadav.
South Africa: Dane van Niekerk (captain), Trisha Chetty, Moseline Daniels, Yolani Fourie, Lara Goodall, Shabnim Ismail, Marizanne Kapp, Ayabonga Khaka, Marcia Letsoalo, Lizelle Lee, Sunne Luus, Mignon du Preez, Chloe Tyron, Laura Wolvaardt.