Pennetta recorded a 6-4, 6-4 decision over Aravane Rezai, setting up a semifinal meeting with Tathiana Garbin.
Garbin, who won this tournament three years ago, was an easy 6-2, 6-1 winner over Olga Govortsova.
The other semifinal will send Errani against Anna-Lena Groenefeld, who advanced when second-seeded Patty Schnyder retired in the first set. Schnyder was coming off a runner-up finish last week in Budapest.
Errani, who won last year's championship match over Mariya Koryttseva, defeated Yaroslava Shevdova 6-2, 7-5 to reach the semifinals.