The collapse began without a run on the board after losing the prized scalp of Stafanie Taylor for a duck to Marizanne Kapp, the slow medium bowler.
Kapp, who finished with two wickets for 17 runs made early inroads by also removing frontline batter Juliana Nero for seven.
At one stage, Aguilleira’s side was precariously placed at 24 for the loss three wickets and her dogged efforts to spark a middle order recovery were futile.
Apart from Deandra Dottin who scored 26, Kycia knight 19 and Shanel Daley 14 no other West Indian batter got into double figures.
19-year-old leg-break bowler van Niekerk was a thorn in the side of the middle order snapping up wickets and cleaning-up the tail-enders as well.
Niekerk bagged five for 28 runs including the important wickets of Dottin and Shemaine Campbelle.
Earlier, powerful top order batting, including a half-century from opener Trisha Chetty, helped set up a challenging South African total of 206.
Chetty top-scored with 57 which included five boundaries while Mignon du Preez scored 48, and Shandré Fritz 24.
The leading West Indian bowlers were Shaquana Quintyne 2-30, Shanel Daley 2-33.
West Indies and South Africa women meet in the second one-day international tomorrow at Warner Park.
SOUTH AFRICA innings
S. Fritz run out 24
T. Chetty b Daley 57
M. du Prez c and b Taylor 48
M. Kapp c Mohammed b Daley 10
S. Benade run-out 5
C. Brits c Daley b Quintyne 11
D. van Niekerk c Smart b Mohammed 9
Y. Potgiter c Nero b Quintyne 17
C. Tyron not out 3
S. Loubser not out 10
Extras: (b-2, lb-2, w-6, nb-2) 12
Total: (8 wkts, 50 overs) 206
Fall of wickets: 1-49, 2-118, 3-147, 4-150, 5-165, 6-165, 7-185, 8-188.
Bowling: Selman 3-0-17-0, Smart 4-0-27-0, Dayley 9-0-32-2, Taylor 10-1-32-1, Mohammed 7-0-28-1, Quintyne 10-0-30-2, Campbell 6-0-25-0, Dottin 1-0-11-0.
WEST INDIES WOMEN innings
S. Taylor c wkp. Chetty b Kapp 0
J. Nero c wkp. Chetty b Kapp 7
S. Daley c wkp. Chetty b Benade 14
D. Dottin c Benade b van Niekirk 26
M. Aguilliera c du Prez b Tyron 40
K. Knight lbw b Benade 19
S. Campbelle stp. Chetty b van Niekerk 4
S. Quintyne b van Niekerk 0
A. Mohammed b van Niekerk 0
T. Smart b van Niekerk 0
S. Selman not out 8
Extras: (lb-3, w-5) 8
Total: (all out, 35.3 overs) 126
Fall of wickets: 1-0, 2-20, 3-24, 4-89, 5-92, 6-102, 7-102, 8-102, 9-104.
Bowling: Kapp 7-1-17-2, Benade 7.3-0-30-2, Tyron 8-1-26-1, Lettsoala 2-0-20-0, Loubser 4-3-2-0, van Niekerk 7-2-28-5.