The Dutch FDJ United-Suez rider now leads the Pole by eight seconds ahead of a tense finale on Sunday's final stage.
Stage 8 was a 171.9 km run from Sisteron to Nice with a flat route interrupted by a late climb which the 2023 champion Vollering used to full advantage, dropping Niewiadoma-Phinney on its steepest section.
The 29-year-old Vollering then extended her advantage to 17sec at the Promenade des Anglais finish line, scooping the coveted yellow jersey.
"I can't tell you how much I suffered, but with all the good people I have round me, that made it possible. I gave it everything," said Vollering, who appeared to be exhausted.
"This is proof that if you really believe in something, if you really dream big about something, then it doesn't matter what it needs to take, how much pain it will cost you."
Vollering wins stage five but Reusser maintains lead in Women's Tour de France
The 31-year-old Canyon-SRAM rider Niewiadoma-Phinney, who beat Vollering to the 2024 Tour de France femmes title by the agonising margin of four seconds, also slugged out on a climb day.
But after the finish Niewiadoma-Phinney accused Vollering's team of gamesmanship, by blocking her during Vollering's attack.
"I was annoyed at the beginning of the climb because (Célia) Gery, on purpose, just blocked me to the barriers where I had to stop pedalling," she said after confronting Gery on live tv.
"If they want to compete, they should compete fair play and not look to block me on the barriers because I feel it is so childish. Honestly, I lost all respect for them for that."
Build up to Nice title struggle
Swiss rider Marlen Reusser who took the yellow jersey in Tuesday's time-trial and held on another day, is now in third place 1min 12sec off the pace, with Elisa Longo Borghini at 3min 05sec in fourth.
Defending champion Pauline Ferrand-Prévot withdrew Saturday morning due to illness after having struggled to the finish line on Friday over 10min down at the line.
Fellow French rider Maëva Squiban – who won two stages last year – attempted to repeat her feat from Chambéry, where she triumphed after a long-range breakaway, but she slipped and crashed on the descent of the Côte de Colomars with 17 kilometres to go.
Women's Tour de France pits France's Ferrand-Prévot against history
Puck Pieterse of Fenix-Premier Tech still leads the polkadot climb points rankings, Antonia Niedermaier of Canyon-SRAM leads the best young rider's standings and Lorena Wiebes retains the green sprint points standings she has led since the opening day.
The race ends in Nice on Sunday with a 99-kilometre stage in the hills outside the Riviera city, with a series of four climbs of the same steep 7km Col d'Eze.
(with AFP)



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