The Polish world No. 2 defeated the third-seeded American 6-0 7-5 to secure her second straight win at the eight-player event in Mexico, news outlets reported.
Świątek opened her WTA Finals campaign with a 7-6 6-0 victory over the Czech Republic's Marketa Vondrousova.
She will now take on Tunisia's Ons Jabeur in her last group-stage match on Friday.
The 2023 WTA Finals event began on October 29 and runs until November 5.
The Polish star last month won the China Open tournament in Beijing, claiming her 16th career singles title.
Świątek in September lost her world No. 1 spot to Belarusian Aryna Sabalenka after spending 75 weeks on top of the world rankings.
The Pole has a chance to regain her world No. 1 ranking depending on her result at the season-ending championships, Polish state news agency PAP reported.
(gs)
Source: IAR, PAP, wtatennis.com