Last year's wooden spooners crushed the Scorchers at North Sydney Oval on Wednesday night, securing the win with 22 balls to spare, to advance to Saturday's decider.

Captain Meg Lanning's decision to bowl first paid dividends, with the Stars restricting dangerous openers Beth Mooney (27) and Sophie Devine (12) before running through the Perth line-up.

Spinner Alana King had the middle-order in knots and took the key wickets of Mooney, Devine and England international Amy Jones to finish with economical figures of 3-16.

Former Australia batter Nicole Bolton saved some face for Perth, compiling a vital 32 to help the Scorchers post 8-125 from their 20 overs.

The Stars experienced some nervous moments, particularly when medium-pacer Heather Graham clean-bowled Lanning (22) with a stunning seaming delivery.

But English allrounder Nat Sciver (47 not out) and teen sensation Annabel Sutherland (30 not out) guided the Stars home with a commanding 67-run partnership.

The Stars, who had previously never finished a season higher than fifth, will take on the winner of Thursday night's semi-final between two-time defending champions Brisbane Heat and the Sydney Thunder in the final.

"To finish top of the table in the round games and now through to the final is unbelievable, and you can't wipe the smile off my face," player-of-the-match King said.

"If someone told me before the game you'll take the top-three (wickets), absolutely you would take that.

"I don't think we will be too bothered on who gets through (to the final), they're two really good teams."

Australian Associated Press