Errani, who won last week's WTA Tour event in Palermo, Italy, next faces third-seeded Caroline Wozniacki of Denmark, who beat Russia's Vera Dushevina 6-0, 6-1.
Wozniacki won 80 percent of the points on her first serve, faced only three break points and needed only 54 minutes to defeat Dushevina.
The other semifinal will pit No. 4 seed Anabel Medina Garrigues of Spain against 19-year-old German Julia Goerges.
Medina Garrigues converted five of 14 break chances and faced only one break point herself in beating Russian Elena Bovina 6-3, 6-2.
Goerges reached the semifinals of a WTA Tour event for the first time since Stockholm last year, beating Petra Martic of Croatia 6-3, 4-6, 6-4 in a match that had 11 breaks of serve - six by Goerges - and took over two hours to complete.
BJORN MISSES LIMERICK EVENT
Goerges upsets Srebotnik in Slovenia Open
WORLD MATCH PLAY SET FOR CHANGE
