Svitolina won her maiden title here last year, and became the only teenager to triumph on the WTA tour in 2013. She could yet repeat the feat, as she doesn't turn 20 until September, but has to get past 2010 French Open champion Francesca Schiavone on Saturday.
Schiavone reached her first semfinals since September when she beat Kristina Mladenovic 6-3, 4-6, 6-0, avenging a three-set defeat to the Frenchwoman last week in Istanbul at the same quarterfinals stage.
The other semifinal features 2012 champ Bojana Jovanovski of Serbia against Stefanie Voegele of Switzerland, who passed the quarterfinals for the first time this season. Both took more than two hours to prevail.
Jovanovski defeated Japanese qualifier Misa Eguchi 4-6, 7-5, 6-3, while Voegele beat 2013 runner-up Shahar Peer of Israel 6-2, 2-6, 6-4.