The all-rounder took 2/27 and blasted an unbeaten 81 off 45 in the chase to guide her ladies to a win that kept their World Cup dream alive
Wife and teammate Dane van Niekerk was full of praise for Kapp, who partnered with Tazmin Brits for 97 runs to break the back of the 158-run chase.
"It kept us alive in the World Cup and that's a fact," she told ESPN.
"That partnership had to win us the game. If that partnership happened we probably wouldn't have gotten over the line. We were chasing 10s for 10 overs and it was nerve-wracking but when we chatted about it afterwards, what stood out for me was how clear she was, and how she knew exactly what they were going to do. That's a different zone to get into as a cricketer. If I knew that while I was sitting there, I'd probably have been a bit more chilled but it was amazing. It was stupid, in the best way."
What made Kapp's performance even more impressive was the fact that she was coming off an illness.
"I would have pulled her out," admitted van Niekerk.
"I saw what she went through before the game. She was short of breath, she was pale and her eyes were glassy so it was a bit scary. But she's in very good hands with the team doctor and the doctor will never let her play if she can't."
South Africa face the Netherlands in their fourth match of the tournament - another must-win encounter - in Bristol on Thursday night. The Proteas Women also need to increase their Net Run Rate to increase their chances of making the semifinals.
Marizanne Kapp is the only Proteas player selected in the ICC Women's T20 World Cup team of the tournament, a trophy won by Australia when they beat England in the final at Lord's on Sunday.
The Proteas Women fell to a 40-run defeat against host nation England in the ICC Women's T20 World Cup semifinal at the the Oval on Thursday.
The South African Women were made to work hard for runs as they eventually chased down 117 to defeat Bangladesh by four wickets in the Women's T20 World Cup at Lord's on Sunday.
The Proteas Women revived their ICC T20 World Cup campaign with a two-wicket victory over Pakistan in their Group A encounter at Edgbaston on Wednesday.
