Other results this weekend meant the Saints' spot in the top-eight was already safe entering Sunday's match at RSEA Park.
But the 10.12 (72) to 4.3 (27) loss, in hot conditions, means their maiden AFLW final will be held in Adelaide instead of Melbourne.
The Crows beat Fremantle later on Sunday, leapfrogging the Saints into sixth to set up an elimination final showdown.
The Saints' day grew even worse when they lost star veteran Jaimee Lambert to a suspected calf injury at the start of the final quarter.
St Kilda have already been badly hit by injuries this season, with eight players currently sidelined, including Nicola Barr, Nicola Xenos and Bianca Jakobsson.
After a tight opening term, the Bulldogs gradually pulled away in the second and third quarters to stun the strong pro-Saints crowd.
The Bulldogs blitzed St Kilda out of the middle, winning clearances 31-14 to create a huge inside-50 advantage.
It was a genuine team performance from the Bulldogs, but Emma McDonald was outstanding up forward with two goals.
Captain De Berry, who was dropped earlier in the season, was able to join the party in the last quarter with two goals.
J'Noemi Anderson (two goals) was a constant threat up forward for St Kilda, while Serene Watson found plenty of ball.
The Bulldogs finish the season 12th with a 5-7 record and starting to show significant promise for the future.
It was their equal highest score of the season.
"It is great for us to finish like that," Bulldogs star Ellie Blackburn told the Seven Network.
"It is an improvement on last season and we know where we are at.
"We are realists and we think it's a good building block for us.
"So it fills us with confidence moving forward."
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