The win sets up a re-match against the USA on Tuesday night at 8.15pm AEST, the only team to get the better of the Devils so far this tournament.
Coming into the Semi-Final as underdogs, Australia's disciplined defence was outstanding throughout the game and never let Great Britain get on a roll.
Shooting 44% for the tournament coming into the match, Great Britain managed just 17-75 (22%) from the field against the Devils and while they put up 27 more shots, they finished with one less make than Australia overall.
"The way the girls executed for the full 40 minutes, you can't ask for much more than that," said head coach Stephen Charlton.
"We had a game plan and maybe three or four times we didn't execute it, otherwise we followed it to a T. The trust they had in each other, it was pretty good to watch."
At the offensive end of the floor, the Devils had their own issues getting the ball over half-court against Great Britain's full-court press but when they were able to get open space, they did not waste their opportunities.
Annabelle Lindsay had the hot hand, scoring nine points in the opening term and coach Charlton's gamble to keep her on the floor with two quick fouls paid dividends.
Lindsay's combination with Teisha Shadwell saw the two big's play all 40 minutes of the contest and they stuffed the stat-sheet as Lindsay finished with 20 points, 26 rebounds, three assists and a block while Shadwell almost recorded a triple-double with 12 points, 19 rebounds, nine assists and a block.
Maryanne Latu also played a crucial role, scoring the first and last baskets of the game while a three-point opportunity early in the fourth quarter halted any momentum Great Britain had as they looked to make one final run.
Australia's game-high lead of six came just before half-time but Joy Haizelden breathed life into the defending Champions with a three-point buzzer-beater.
The Devils responded with a 6-2 run to begin the third term though and Latu had another timely make just before three-quarter time to keep Australia's noses in front.
Their strict defence ensured Great Britain were only able to put up mid-range shots in the fourth quarter and that did not help their shooting percentages.
With four points the difference in the last 12 seconds, Haizelden was fouled beyond the arc but she only hit one free-throw which Lindsay cancelled out with her own free-throw at the other end.
Latu then put the exclamation mark on the win, getting a lay-up in the dying moments off a clever out of bounds misdirection play that saw the lane open up for her.
Find the box score here and watch the replay below.
The Devils now look to put in a similar performance against the USA in the gold medal game after falling to them in the group stage, 31-56.
Having claimed silver medals in 2011 and 2015 at the IWBF Under-25 World Championships, they will at least equal the results of those teams but will be desperate to break through for a maiden gold medal.
The Australian Devils schedule for the 2019 IWBF U25 World Championships (all times AEST):
May 23: Devils def. Germany 55-37
May 24: Devils def. Turkey 53-24
May 25: Devils def. by USA 31-56
May 26: Quarter-Final- Devils def. South Africa 72-12
May 27: Semi-Final- Devils def. Great Britain 42-36
May 28: Gold medal game- Devils vs. USA at 8.15pm