Meg Lanning hit a composed 55 and Alyssa Healy a rapid 25 as Australia compiled 132-6 amid a mixed England fielding performance.
In reply, Charlotte Edwards (31) and Tammy Beaumont (32) added 67 for the first wicket inside 10 overs.
But from there, England lost regular wickets to slump to 127-7.
Australia – seeking a fourth straight title – will play New Zealand or West Indies in the final in Kolkata on Sunday.
England, meanwhile, miss out on the final for the first time since 2010. (Courtesy BBC Sport)