England got off to a strong start of 1-55 but after a collapse managed just 8-105 from their 20 overs.
Heather Knight top-scored with 29 while Aussie bowlers Sarah Coyte claimed 3-16 and Ellyse Perry took an economical 2-13.
After winning the toss and sending their opponents in paid dividends, the defending champions set about running down their Ashes defeaters total with the bat.
Aussie captain Meg Lanning dominated the England attack on her way to 44 off 30 balls but annoyingly lost her wicket with victory within one shot.
Alex Blackwell then fell for a duck but the damage had been done and scenes of elation followed when all-rounder Perry (31) hit the winning runs.
Australia last met England in the final in 2012 when they won by four runs, but this was a far more convincing affair with the results hardly ever looking in doubt.
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