Sian Ruck cut a delivery from Anisa Mohammed in the 45th over and attempted to steal a single. The non-striker Rachel Priest, guilty of ball watching, was caught well outside the crease and even before the umpire could lift his finger, the jubilant West Indies team had started celebrating.
Merissa Aguilera's girls had just beaten New Zealand by 48 runs in the Super Six game of the Women's World Cup on Monday and put themselves in a strong position to face Australia in the final.
Having heavily relied on all-rounder Stafanie Taylor and hard-hitting Deandra Dottin in the tournament, the team benefited from collective contributions, for a change.
The Kiwis, chasing a modest total of 208, floundered against the Caribbean bowling. Spinners Mohammed and Taylor combined to take three wickets and gave away just 39 runs in 18.3 overs. Tremayne Smartt, opening the attack, scalped three key wickets to give the side the momentum.
Skipper and opener Suzie Bates scored 30 and Priest chipped in with 36 down the order, the only noteworthy contributions for the side.
New Zealand, choosing to field after winning the toss, were in control of the game until the final session of the West Indies batting.
The former champions threw away the opportunity to dismiss the opposition cheaply after having them at 159 for eight at one stage. Shanel Daley (37) and Mohammed (31 n.o.) displayed grit to add 45 runs for the ninth wicket.
West Indies, with six points, take on Australia next while New Zealand take on England, who have four points apiece. The net run-rate will be crucial for deciding the second finalist.
Brief scores: West Indies 207/9 (S Taylor 49, S Daley 37; M Nielsen 3/37) v New Zealand 159 in 44.3 (R Priest 36, S Bates 30; T Smartt 3/39)