Following South Korean Min A Yoon's triumph in Rosebud last week, veteran Smith topped the competition with a five-shot victory, finishing at 20 under.
Victorian Andrew Martin (66) and Queenslander Shae Wools-Cobb (67) tied for second.
Smith became the fourth female golfer to win a mixed-gender event on a recognised professional tour, with Hannah Green making history as the first when she won the same tournament last year.
A regular on the LPGA for a decade, Smith only has limited status this year after a slow return following the birth of her son Theo in 2019.
The 38-year-old Queenslander, who finished tied for fifth at the 2018 US Open, set up the win with a sizzling third round when she surged up the leaderboard with an eight-under 63.
She entered the last day tied for the lead at 14-under with Victorian Matias Sanchez, who led by three shots at the halfway mark.
But Smith kept the field at bay on Sunday with a bogey-free round of six-under, relishing her improvement since linking with Cameron Smith's coach Grant Field late last year.
"I'm happy with the week obviously - I was so far from this two months ago that I couldn't have even dreamt of this right now," Smith said.
"I'm incredibly proud of the work we've done and excited now for everything to come."
Martin threatened early, picking up four straight birdies to open his final round before dropping a shot on the seventh.
He collected another three birdies on the back nine and a dazzling eagle on the 13th.
But his momentum stalled with a double bogey on the 15th thanks to a wayward tee shot that required him to hit a provisional ball before a bogey on the 16th further soured his run.
Smith, meanwhile, stayed ultra consistent, peppering her round with six birdies and 12 pars.
Sanchez was even for the final round to finish fourth.
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