Panova came away a 2-6, 7-6 (7-5), 6-4 winner over Nina Bratchikova. It was the fourth quarterfinal Thursday that went three sets after the eventual winner dropped the first set.
Bratchikova was serving for the match at 5-4 of the second set but Panova broke back to even the set and eventually force a tiebreaker. Panova had four breaks in a seesaw third set, including taking the final break in a series that put her up 5-4.
No. 5-seeded Bojana Jovanovski, who will go against Panova in Friday's semifinals, defeated Aleksandra Krunic 5-7, 7-6 (7-3), 6-3 in a battle that took 3 hours, 16 minutes. Jovanovski had three breaks in each set.
The other semifinal features a pair of unseeded players. Julia Cohen advanced with a 3-6, 6-3, 6-4 win over Magdalena Rybarikova and Olga Puchkova ousted third-seeded Mandy Minella 2-6, 6-1, 6-2.