With the three-match 50-over series currently level at 1-1, following the South Africans' emphatic 40-run victory at the Three Ws Oval in Barbados on Saturday.
Today's clash at the same venue presents an opportunity to decide the outright winner, and Shangase stresses a replica of their performance over the weekend will be crucial.
"We know what's at stake here, and we're ready for Tuesday, we just need to perform at our best again to make sure we get over the line," said Shangase.
With coach Mandla Mashimbyi's charges having amassed a 309-run total, the 29-year-old registered her maiden international half-century in an 85-run third-wicket partnership with Sune Luus, and reflected on how special a moment it was for her.
"It means a lot to me, I've been trying to get it, and upon getting it, I was really emotional," said Shangase.
"At the same time, I [had to remind myself] it's still not over, the game is still on, and I still need to wipe those tears and go back to carry on with the match.
"But it really meant a lot to me. It was [special]."
The Dolphins Women player has notably stepped up with the bat in recent matches, but she insists her love for bowling has not changed as she continues to work on both aspects of her game.
"At the moment, batting is in front now, and judging from both – I can't judge, it's two different skills and I love them both," she acknowledged.
The Proteas Women are ramping up preparations for the upcoming ICC Women's Cricket World Cup set for India and Sri Lanka in September, with the Windies having missed out in the qualifiers to Bangladesh Women.