Peterson, 24, broke her Kazakh opponent five times and smashed 13 winners in a match that lasted exactly one hour.
Fatigue seemed to play a part for Rybakina, who was involved in three-setters in both her quarter-final and semi-final matches that finished late.
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The 20-year-old made 11 unforced errors and won only 48% of her first service points in the final. In contrast, Peterson won 83% of her first service points.
Peterson was also aided by Rybakina's double fault in the opening game of the first set that immediately swung the momentum in the Swede's favour.
Although Rybakina tried to dictate rallies using her power, it was Peterson who finished off points, winning nine straight games to bagel the fourth seed in the second set and clinch the title.
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