With Deandra Dottin retired and Stafanie Taylor unavailable owing to injury, skipper Hayley Matthews’ opening partner was Natasha McLean but she was dismissed for a first ball duck by Fran Jonas with one that came in with the arm.
West Indies pushed Aaliyah Alleyne, who played a match-winning end in the third ODI, up to number three to take advantage of the fielding restrictions in the Powerplay.
Jonas bowled tightly in the Powerplay and amped up the pressure but Alleyne was fluent against the pacers and kept the score ticking by running hard between the wickets and also scoring prolifically behind square on either side of the wicket.
Matthews eventually fell for 15 off 23 balls after driving one straight to Suzie Bates at cover as Amelia Kerr struck. Jonas then increased West Indies’ woes as she bowled Chedean Nation for just two.
Alleyne played well to get to 49 but could not get to her first fifty as she was bowled by Kerr while trying to cut one off the stumps.
West Indies’ collapse continued after that as Kyshona Knight was run out for four by a direct hit from short third by Hannah Rowe.
The hosts running continued to be catastrophic as they lost as many as three wickets to run outs, with Shakera Selman being the last one off the final ball of the innings.
West Indies folded for 115 as Kerr finished with three for 16, while Jonas returned two for 13 as the spinners strangled the batters.
West Indies put up a spirited effort with the ball as Chinelle Henry dismissed Suzie Bates LBW after she charged down the track but failed to connect. Georgia Plimmer was promoted to no.3 but she failed to impress as she fell for just two to Matthews.
Henry then struck a big blow as she accounted for Sophie Devine, who fell on the pull for 24 off just 18 balls. Henry then got the prized scalp of Kerr, who was the Player of the Series in the ODI leg, for just three as she could only lob a return catch to her off the leading edge.
New Zealand were soon in freefall as the in form Maddy Green needlessly ran herself out for 11 in the same over after getting off to a fast start. McLean had dropped a catch earlier behind the wickets but she nailed the direct hit to run Green out.
The spin duo of Karishma Ramharack and Afy Fletcher then ran through the lower order as West Indies emerged victorious after successfully defending a low total after Row gave them a late scare by going ballistic in the final over against Alleyne with 20 needed. Rowe tried valiantly but fell just short, managing 18 off the over after swatting a six over long on off the final ball.
Brief Scores: West Indies 115/10 in 20 overs (Aaliyah Alleyne 49; Amelia Kerr 3/16, Fran Jonas 2/13) beat New Zealand 114/9 in 20 overs (Hannah Rowe 26*; Chinelle Henry 3/26, Afy Fletcher 2/18) by one run