Two-time champion Annemiek van Vleuten took the overall La Vuelta Femenina lead with one stage remaining after finishing second in Larado.
Italy’s Gaia Realini, 21, beat the 40-year-old Netherlands rider in a sprint finish for her maiden tour-stage win.
But Van Vleuten opened a lead of one minute 11 seconds in the general standings.
Demi Vollering, who started the sixth stage with a five-second lead, is second overall after finishing fifth.
Van Vleuten, who is aiming for a third consecutive title, attacked 36km from the finish and broke up the peloton over the day’s two climbs.
Her compatriot Vollering had been left behind after stopping for a comfort break in crosswinds and was unable to bridge the gap in time to track the Movistar rider’s move.
Vollering finished one minute four seconds back as part of a reduced peloton that included Claire Steels, the first Briton home in 16th place.
Lizzie Deignan, who recently returned to racing following the birth of her second child, was 39th, more than eight minutes behind the leading pair.
Sunday’s seventh and final stage features a mountain-top finish in Lagos de Covadonga.
Stage six results
1. Gaia Realini (Ita/Trek-Segafredo) 2hrs 49mins 23secs
2. Annemiek van Vleuten (Ned/Movistar Team Women) same time
3. Loes Adegeest (Ned/FDJ-SUEZ) +1min 4secs
4. Silvia Perisco (Ita/UAE Team ADQ) same time
5. Demi Vollering (Ned/Team SD Worx) same time
6. Mavi Garcia (Spa/Liv Racing TeqFind) same time
7. Evita Muzic (Fra/FDJ-SUEZ) same time
8. Katarzyna Niewiadoma (Pol/CANYON/SRAM Racing) same time
9. Riejamme Markus (Ned/Team Jumbo-Visma) same time
10. Ane Santesteban (Spa/Team Jayco-AlUla) same time
General classification
1. Annemiek van Vleuten (Ned/Movistar Team Women) 16hrs 16mins 17secs
2. Demi Vollering (Ned/Team SD Worx) +1mins 11secs
3. Riejamme Markus (Ned/Team Jumbo-Visma) +1:23
4. Juliette Labous (Fra/Team DSM) +1:58
5. Marlen Reusser (Swi/Team SD Worx) +2:11
6. Olivia Baril (Can/UAE Team ADQ) +2:18
7. Katarzyna Niewiadoma (Pol/CANYON-SRAM Racing) +2:38
8. Mavi Garcia (Spa/Liv Racing TeqFind) +2:39
9. Erica Magnaldi (Ita/UAE Team ADQ) same time
10. Ricarda Bauernfeind (Ger/CANYON-SRAM Racing) +2:45
