Germany's Annika Beck knocked out defending champion Mirjana Lucic-Baroni in the semi-finals of the Coupe Banque Nationale on Saturday.
The 21-year-old Beck started strongly, breaking twice to take the first set 6-2, but Lucic-Baroni hit back to take the second set by the same margin.
True to the topsy-turvy nature of the game, Beck then responded by claiming two more breaks for a 3-0 lead in the third set.
Lucic-Baroni regained one of those lost breaks but then surrendered her next service game before Beck held serve to open up a 5-1 lead.
The eighth game was a long one, with Beck letting three match points slip before her opponent finally clinched her fourth break point opportunity.
But Beck still had a break in her hand and she made no mistake with her next service game to seal a 6-2 2-6 6-4 victory.
Awaiting Beck in Sunday's final is Jelena Ostapenko, who beat Great Britain's Naomi Broady 6-4 6-2 earlier in the day.
"Already, before the match I knew she was a really good server so I would have to win all my service games," Ostapenko told WTA Tennis. "I tried to play aggressive and I was playing quite smart – not trying to go for every ball.
"If I play my best tennis I can win the final. But you just have to play your best and not expect anything."