Gilmore looked down and out in her semi-final clash with arch rival Carissa Moore but stunned with a powerful final-minute ride to score 7.67 to overtake the top-ranked Hawaiian.

Gilmore hadn't been past the quarter-finals in this year's three Tour events and had never made a final at Margaret River before.

She will meet in-form Tatiana Weston-Webb in the final later on Monday after the Brazilian accounted for local hope Bronte Macaulay.

Macaulay put aside the heartbreak of losing her younger brother Jack on the weekend to contest the final four heat.

Jack, a noted surfer himself, passed away suddenly, leaving the popular West Australian surfing family devastated.

It was unclear if Macaulay, who grew up in nearby Gracetown, was going to compete on Monday but she showed her bravery to suit up.

Older sister Laura was a former Championship Tour competitor while father Dave was a former professional surfer, ranked as high as third in the world in the late 1980s and early '90s.

The father of four now works as 27-year-old Bronte's coach and board shaper.

Gilmore said the surfing fraternity was thinking of the Macaulay family.

"We really love you, the Macaulays, you're the sweetest, coolest family in the world," Gilmore said after her semi-final win.

"Bronte, it was incredible courage to show up this morning, just so strong, and we're sending you all the love in the world so I hope you're feeling it."

Aiming to make her maiden WSL final, Macaulay, ranked world No.11, posted an opening 6.00 to the cheers of a large hometown crowd.

But despite her best efforts in the two-metre conditions Macaulay was only able to add a score of 3.00 as her Brazilian opponent advanced to the final.

Weston-Webb nailed the highest score of the heat with a 7.15 for a combined 12.27.

Australian Associated Press