The 17-year-old, playing in only her 10th international in the sport's shortest format, hit a composed and fluent 35 off 34 balls as Sri Lanka posted 129-4 batting first at Newlands on Friday. South Africa finished on 126-9 in their 20 overs.
A spirited counterattack from captain Harmanpreet and Rodrigues went in vain as Australia entered their 7th Women's T20 World Cup final with a five-run win over India in the first semi-final at Newlands Cricket Ground on Thursday.
Fantastic unbeaten knocks by Jemimah Rodrigues (53 not out off 38) and Richa Ghosh (31 not out off 20) led India to an impressive seven-wicket win over arch-rivals Pakistan in their opening match of Women's T20 World Cup 2023.
The left-handed 26-year-old was the first lot on the block at the sale in Mumbai, and was the object of a bidding war. Nita Ambani placed several bids for Mandhana's services before the Royal Challengers Bangalore prevailed.
The bespectacled 25-year-old, whose previous highest in T20 cricket was 43, clubbed 14 fours in her 68-ball innings to give Pakistan a great chance of collecting their first win of the competition.
Sri Lanka were restricted to 112 for eight after being sent in to bat in overcast conditions. It never looked nearly enough as Mooney (56 not out) and Healy (54 not out) scored freely from the start of the innings.
Sciver-Brunt and England captain Heather Knight (28) put on 51 for the fourth wicket with aggressive batting, while Amy Jones hit strongly later in the innings to make 40 off 27 balls with two sixes and three fours.