Kapp bowled a tempting line outside off stump, swinging the new ball away from Matthews, who having struck one four through the covers, edged the penultimate ball of the third over, to give wicketkeeper Sinalo Jaftha an easy catch.
Dottin had struck three boundaries to get to 13, and it was a surprise that Wolvaardt didn’t give Kapp the over immediately after she’d arrived at the crease, following the dismissal of Qiana Josephs, who looked out of her depth and was Mlaba’s first wicket.
But Kapp bowled the first over after the power play and with her fifth delivery induced a false drive from the self proclaimed ‘World Boss’ giving Wolvaardt a simple catch in the covers.
The rest of the innings was about controlling the remaining West Indies batters, which the Proteas managed well, even if some of their fielding was sloppy.
Mlaba bowled a magnificent 12th over, bamboozling Shemaine Campbell, and dismissing her with a delicious arm-ball, to end a 30-run partnership with Stafanie Taylor.
Mlaba had Chinelle Henry caught behind first ball and claimed her fourth wicket with help from an excellent diving catch in the covers by Brits to get rid of Aaliyah Alleyne at the start her final over to finish off a match-defining spell.
Kapp was her usual thrifty self, taking 2/14, her spell included 17 dot balls.
Taylor was the West Indies top scorer with an unbeaten 44 off 41 balls, but she struggled with the heat, and could barely run in the latter stages of her innings.
Wolvaardt admitted afterwards that she found conditions difficult too, but was grateful for her bowlers efforts in limiting the West Indies to a below par total.
While Brits battled with her timing initially, the South African captain led the charge during her team’s power play, hitting six of the seven fours while the fielding restrictions were in place.
She finished on 59, hitting seven fours, and Brits after eventually coming to terms with pace of the surface, struck an unbeaten 57, that included six fours.
The win sets up the Proteas for a spot in the semifinal and relieves the pressure ahead of the second match on Monday against a powerhouse England side.