Gauff served big and played sensational defence en route to a 7-6(2), 3-6, 6-4 win over the Pole and will face Czech Karolina Muchova (26) in Sunday's final after Muchova defeated Aryna Sabalenka (25) 7-6(4), 6-3, 6-2.
Gauff leapt into the air and pounded her chest as the crowd erupted after she secured the hard-fought victory.
"I knew playing her was going to be tough, nothing was going to be given to me today," she told Tennis Channel.
"I took my opportunities when I got them and just fought for every point. I was a little negative in the second set but I got it back and I was just telling myself, 'You're a warrior, you can do this.'
"This shows that I can do it. A lot of people had doubts about my game but I'm still developing."
Those doubts peaked when she was sent packing in the opening round at Wimbledon last month.
"I told myself I can either let this crush me or make me rise and I decided to make myself rise from it," she said.
Gauff has certainly elevated her game since the start of the US hard court swing, winning the title in Washington DC, making the quarters of the Canadian Open and now reaching her first final of a WTA 1000 event.
