Tauson topples Alexandrova again in Luxembourg
Vondrousova and Cornet also advance in Luxembourg while Putintseva wins in Portoroz
The 18-year-old defeated the same opponent en route to claiming a maiden WTA Tour title in Lyon in March and repeated the feat here, again on an indoor court.
On this occasion, Clara Tauson needed to come back from a break down in the deciding set to clinch a 6-4, 3-6, 7-6 (7-1) triumph and book her spot in the quarter-finals.
Fifth seed Marketa Vondrousova had no such trouble – the Czech was a comfortable 6-2, 6-4 winner over Jana Fett. Eight seed Alize Cornet also made the last eight with a 6-3, 6-3 win over home favourite Mandy Minella, while Ludmilla Samsonova, the seventh seed, needed a pair of tie-breaks to overcome Oceane Dodin.
In first-round action, sixth seed Zhang Shuai lost in three sets to Marie Bouzkova.
At the Zavarovalnica Sava Portoroz in Slovenia, second seed Yulia Putintseva was a 6-3, 6-1 winner over Katie Boulter. Third seed Alison Riske, Frenchwoman Kristina Mladenovic and qualifier Lucia Bronzetti also made it through in round of 16 action.