The Southern Stars set 5-140 from their 20 overs, with opener Elyse Villani top scoring with 35.
In response the Windies women looked dangerous, with Deandra Dottin (40) and Stacy-Ann King (36 not out) banding together. But they ultimately fell short with 20 from the last 10 balls proving too much.
In the final they will play England or South Africa, who meet on Friday.
Australia’s women have won the past two World T20 finals, beating New Zealand in 2010 and England in 2012 by three and four runs respectively.
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