The tournament's leading wicket-taker snared 4-23 in the breezeless 38-degree conditions which forced teammate and Southern Star in waiting Ashleigh Gardner from the field with heat exhaustion midway through the Scorchers' run chase, a precaution taken after the head knock she suffered at training on Friday.

English veteran Katherine Brunt (35 not out) tried valiantly to heave her team over the line in front of 2726 fans as they chased the Sixers' seemingly below-par 5-124 and left Perth with 16 required off the final over but it proved a bridge too far. It was a brilliant bowling display from the Sixers.

Aley took the spoils but Kim Garth's 1-20 from four overs tightened things up and Lauren Smith stepped up to bowl three crucial overs in the absence of Gardner, following her match-turning run-out of Perth skipper Suzie Bates in the 11th over.

"I said in the change room on the halfway mark that we didn't have enough runs on the board, we didn't bat well enough but we needed to make it enough runs and our bowlers just did the job again as they have been doing all season," stand-in captain Alyssa Healy said.

The Scorchers seemed to be cruising at 1-61 with Nicole Bolton and captain Suzie Bates at the crease, but a brilliant Lauren Smith run-out turned the game on its head.

"She's an absolute jet in the field, she leads our fielding group 99 per cent of the time," Healy said of Smith's contribution.

"She's an amazing player to have in your squad. As soon as it's a big game she just seems to embrace that and come out of her shell."

Soon after the run-out of Bates, Bolton fell for 34 from as many balls off the tight bowling of Garth. She'd been dropped in the first over by Marizanne Kapp off her own bowling and the Sixers celebrated her departure with glee. Enter Aley who had earlier dismissed the dangerous Elyse Villani.

She took full advantage of the expanding required run rate, removing Heather Graham before bowling Chloe Piparo and Anya Shrubsole with consecutive balls in the penultimate over.

"Some might call me a bottle of red wine, getting better with age," Aley said.

"We had clear plans this year of what we wanted to do as bowlers and I guess I kept doing what I was good at and making sure that I was trying to bowl my best ball every time I got the ball.

"For us to scrap and fight through that win, we knew 124 probably wasn't going to be enough but at the end of the day we knew what we had to do."

Earlier on Perth had won the toss and sent the visitors in to bat on a sluggish WACA wicket, the same strip used in Tuesday's women's and men's semi-finals.

The Scorchers' international bowling battery immediately kicked into gear, Englishwoman Shrubsole taking the wicket of Dane Van Niekerk in the second over with the South African captain caught behind by Emily Smith for just one run.

Stand-in captain Healy and Gardner went to work building an innings in the Perth Heat, but struggled with the pace of the wicket which was showing a distinct lack of speed hosting its third game in five days.

It restricted tournament big hitter Gardner's natural game, and after 31 balls she was bowled for 21, sluggish by her standards but an indication perhaps of the unfavourable batting conditions.

Soon after Healy went for 40, but the Sixers didn't panic and some inventive late batting from South African international Kapp helped salvaged the innings and she finished 34 not out from 28 balls.

MOONEY HONOURED

Meanwhile, Brisbane Heat wicketkeeper Beth Mooney has been named WBBL player of the tournament after finishing as its second-highest run scorer.

Mooney had 12 dismissals behind the stumps to go with her 482 runs which came at an average of 43.81 and included five half-centuries.

Only Melbourne Stars captain and Belinda Clark medallist Meg Lanning (502) scored more runs. Mooney finished clear of Hobart's New Zealand import Amy Satterthwaite in WBBL player of the year voting, with Gardner finishing third.