Seven-time Grand Slam winner Venus benefited from nine Serena double faults en route to a 6-7 (2/7), 6-2, 6-3 victory at the USD 2.5 million hardcourt tournament yesterday.
Venus posted her first win over top seed and defending champion Serena since another three-set victory five years ago in Dubai.
"Serena is at her top level," Venus said. "You can't win every match. You can't win them all.
"She's number one. Nobody wants to play her. If you do, you have to play the match of your life."
The contest lasted just over two hours as Venus hammered six aces and had just two double faults.
"Big sister taught little sister a lesson," world number one Serena said.
Many of the crucial points in the semi-final came off second serves as Venus won 56 percent of hers compared to just 36 percent for Serena, who still leads their head-to-head series 14-11.
In Sunday's final, Venus will face third-seeded Agnieszka Radwanska of Poland who beat unseeded Russian Ekaterina Makarova 7-6 (7/1), 7-6 (7/3).
"I want to go out there and perform well," Venus said. "If I am fortunate enough to win this tournament, then I am sure it will be dance-worthy."
This also marked the first time Venus and Serena appeared on the same court together since Serena's infamous wobble at Wimbledon.
Six weeks ago Serena exited Wimbledon in bizarre fashion. Appearing dizzy and bewildered during a Wimbledon doubles match with her sister as she struggled just to bounce the ball and then double-faulted four times in a row. Serena later blamed her performance on a virus.
