The toss was held after a delay of nearly three-and-a-half hours due to rain and the match has been reduced to 42 overs per side.
But, Australia have not become the best in the world by going down without a fight and when Villani was dropped on 10 by Shikar Pandey she made the most of her second life.
The India vs Australia, ICC Women's World Cup 2017 Semi-final Match will start at 03:00 PM IST, Saturday, July 20, 2017. The Chandigarh girl scored her third ODI hundred in the 35th over in just 90 balls.
India, though, have not won the World Cup, and will kook to do so as a fresh challenge awaits them.
Sharma was then dismissed by Villani, ending a partnership that produced 137 runs from just 12.3 overs with Kaur scoring 106 of them.
Australia, meanwhile, is in sublime form and would hope to enter their ninth World Cup final.More news: Dennis Hastert out of federal prison
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Australia played a bowler short throughout the tournament, insisting on packing their side with batters and backing themselves to chase down anything.
Mithali lost her wicket at a vital stage in the 25th over of the match with 101 runs on the board.
The winners will face England in the final at Lords on Sunday after the hosts beat South Africa in Bristol.
"Once the players display something that they are not used to, it gives them a lot of confidence that even they are capable of", she added, reflecting on the "heartwarming" performance against New Zealand.
India, who reached their only previous final in 2005, had experienced a disappointing start of their own as they sunk to 101-3, including the dismissal of inspirational captain Mithali Raj for 36.
The victor of tonight's match will play England in Sunday's final at Lord's. In the past 42 times that India has played Australia in One Day Internationals, Australia has won 34 and India has won eight matches.
Australia's top order has been consistently strong throughout the tournament, only being bowled out once, but opener Beth Mooney said herself and Nicole Bolton enjoy knowing Perry can come in and go on with it if they need.