Mills managed just one WBBL game during her two years at the Brisbane Heat after being stuck behind Jess Jonassen and Amelia Kerr in the spinning pecking order.

But the 20-year-old has become a surprise star at the Scorchers this season, snaring 16 wickets at an average of 12.81 to help lift her side into Saturday's decider against the Adelaide Strikers.

Mills looms as a key figure in the final at Perth's Optus Stadium, and she couldn't help but laugh when thinking back to her childhood memories of playing cricket with her siblings.

"I'm one of six kids. It was always pretty competitive around the household," Mills told AAP.

"Obviously being an older sister - I have two younger brothers - I think I might have scared them off cricket a bit.

"We didn't have a massive backyard, so the pitch was quite short.

"I was just a young kid trying to bowl as fast as I could after seeing Mitchell Johnson trying to take the Poms' heads off.

"I don't think we got many backyard cricket matches after that."

Mills made it into the Queensland talent pathway as an allrounder during her younger years, but her ticket into the various teams was as a batter, given the strong bowling line-up already on offer.

Becoming a spinner wasn't on the radar at the time.

"I was bowling one day at training and the coach tapped me on the shoulder and was like, 'why don't you give that (spin bowling) a go?'," Mills said.

"That was about four years ago. Now I've turned into a bowler that doesn't bat much.

"It just goes to show sometimes you haven't found your niche yet."

WA Cricket hope to attract a crowd in excess of 42,000 at Optus Stadium.

If the Strikers prevail, it will be a remarkable achievement given they were involved in elimination finals on Wednesday (beating the Heat) and Thursday (beating the Renegades) before flying to Perth on Friday for Saturday's final.

The Scorchers secured direct entry into the decider after finishing on top of the table.

Australian Associated Press