Chasing close to four runs an over, South Africa openers made sure that they did not lose any wickets early. Andrie Steyn made an 83-ball 41 while Robyn Searle scored 15 runs from 34 balls.
Searle was the first wicket to fall after which the Bangladesh bowlers kept pegging away with wickets at regular intervals.
From 104 for four, they slipped to 110 for eight with Salma Khatun picking up crucial wickets. Since then, they did not recover and was eventually all out for 141 in 44.5 overs.
Earlier, Murshida Khatun and Shamima Sultana got Bangladesh off to a steady start. They added 78 runs before the latter got run out for 34 runs from 45 balls.
They lost two more wickets in quick succession with Nigar Sultana and Murshida getting out in a span of three deliveries. Khatun made a 65-ball 36.
Coming in at number four, Fargana Hoque revived the Bangladesh innings with a patient half-century. While wickets kept falling at the other end, Haque scored an unbeaten 72 from 101 balls and took the team closer to the 200-run mark.
However, they fell short by four runs as Bangladesh finished 196 for nine after 50 overs. Jane Winster was the pick of the bowlers with three for 32 in her nine overs.
Bangladesh 196/9 in 50 overs (Fargana Hoque 72, Jane Winster 3/32) beat South Africa 141 all out in 44.5 overs (Andrie Steyn 41, Salma Khatun 3/25) by 55 runs