Earlier on Friday, Rybakina booked her last-four spot by defeating Italy’s Jasmine Paolini 6-3 5-7 6-3.
On the other side of the draw, Wimbledon champion Marketa Vondrousova knocked out world number two Aryna Sabalenka with a 3-6 6-3 7-5 win.
Sabalenka has failed to go beyond the quarter-finals of a tournament since her Australian Open triumph in January.
The Belarusian, a runner-up in the last three Stuttgart tournaments, committed 48 unforced errors and converted just six of her 15 break points.
Vondrousova, the Czech sixth seed, will play Marta Kostyuk next after the Ukrainian secured her second straight top-10 win against US Open champion Coco Gauff.
American Gauff sped through the first set in 36 minutes, but Kostyuk, who knocked out China’s fifth seed Zheng Qinwen on Thursday, fought back from a break down in both the second and third sets to win 3-6 6-4 7-6 (8-6).
