Dottin claimed 4-22 with the ball and then returned to smash 33 but West Indies, chasing 129 for victory, managed 120-8 from their 20 overs.
New Zealand will clash with South Africa, who stunned defending champions Australia in the first semi-final, in Sunday's final in Dubai, which will produce a new world champion.
Electing to bat at the Sharjah Cricket Stadium, New Zealand could not quite capitalise on their strong start and posted a modest 128-9.
Suzie Bates (26) and Georgia Plimmer (33) put on 48 runs for the opening stand but most New Zealand batters struggled to time the ball.
Dottin ran through their middle order but New Zealand managed to cross the 125 mark thanks to Isabella Gaze's unbeaten 20.
West Indies stumbled early in their innings as Eden Carson grabbed three key wickets to put New Zealand ahead.
Dottin was dropped three times, including twice off Lea Tahuhu, early in her knock which allowed West Indies to crawl back into the contest.
Dottin hit Tahuhu for back-to-back sixes to rub salt into her wound before Amelia Kerr finally dismissed the batter in the 17th over to effectively seal the fate of the match.
Needing 15 runs from the last over from Bates, West Indies managed only six.
"I'm a bit emotional but really proud of the girls," player of the match Carson said.
"When Deandra Dottin was pumping us all over the place I thought 'oh no', but we stuck together, knew we could get it done and we got over the line in the end."
West Indies captain Hayley Matthews said their batters should have done better.
"...with the bat we probably just weren't able to get going early on and that put us under pressure early on," she said.
"We felt that based on the wicket they were probably a few runs short. We wanted to stay positive but we never really got it going."