Kerber, the 2016 Australian Open champion, won four consecutive singles matches at the Hopman Cup, followed by five in Sydney.
In a topsy-turvy match on Friday that included 11 breaks of serve, Barty needed just one in the third set to set up a final against Angelique Kerber or Camila Giorgi.
She will meet the victor of another quarterfinal between defending champion Agnieszka Radwanska and qualifier Camila Giorgi. I'm trying to do my best on court and win as many matches before going to Melbourne.
Kerber eased to a 6-2, 6-3 triumph, reaching the Sydney final for the second time in her career having lost to Tsvetana Pironkova in 2014, and her first in any tournament since April previous year.
Kerber, who began past year as No.1 before finishing at No.22, continued her 2018 resurgence with a thumping 6-3, 6-1 win over Slovakia Dominika Cibulkova.
"To be honest, I felt like I probably played some of the better tennis that I have this week".
"Now that I am No.3 ... the first and foremost thing that I am thinking about and feel like I am capable of doing, regardless of whatever anyone else says".
Kerber was too good. Image Getty
"That has always been (the case) when I have been the No.1-ranked player".
Barty completed a confident 6-3 6-2 victory over Czech Barbora Strycova, while Gavrilova advanced after her last-eight opponent Garbine Muguruza withdrew due to a leg injury.
"It's nice getting a bit of confidence going into our biggest tournament for us", Barty said of next week's Australian Open.
"We have set up a flawless platform for me to work with this year to try and go deep in tournaments, whether it's in Australia or in Europe or in the States".
In men's semifinals, Russian qualifier Daniil Medvedev booked a spot in the final by upsetting fourth-seeded Fabio Fognini of Italy 2-6, 6-4, 6-1.
The 84th-ranked Medvedev came back from a set down to move within one win of what would be his maiden ATP title against rising Australian star Alex de Minaur.
FDA putting new limits on cold medicine for children
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