The top-seeded Aussie, who has led the ranking table for the past 82 weeks, needed an hour and a quarter to move into Sunday's title match, surpassing her semi-final showing from 2019.
Barty will play for the trophy on Sunday against the winner of a later match between Swiss wild card Jil Teichmann -- who beat good friend and Olympic gold medalist Belinda Bencic in the quarter-finals -- and Czech fifth seed Karolina Pliskova, more than a year and a half without a title.
Against Kerber, Barty increased her lead in the series between multiple Grand Slam winners to 4-2 as she duplicated a Wimbledon semi-final victory from last month.
Barty produced a dozen aces as she broke Kerber five times. Her 39 match wins this year nudge her one ahead of Aryna Sabalenka on the WTA list.