Davenport has made it to the semifinals in all three appearances since giving birth to her first child in June. She won the Bali Open in September and has not lost a set in her three matches this week.
Second-seeded Vera Zvonareva earned a semifinal meeting with Davenport by defeating Olga Poutchkova 6-2, 6-1.
Vakulenko was a 6-3, 6-2 winner over Olga Govortsova and Ditty dispatched Vania King 6-4, 3-6, 6-4. It was the first quarterfinal match of Ditty's career.