Parmentier won 6-3 6-4 in one hour and 47 minutes on Saturday to remain on course for the third WTA title of her career and her first since lifting the trophy in Bad Gastein 10 years ago.
Standing in the 32-year-old's way is world No.75 Hercog, who stormed into her first WTA tour final since 2012 after dumping out 48th ranked Maria Sakkari (Greece) 6-4 6-2 in 89 minutes.
Hercog, who returned to action last May after eight months on the sidelines with injuries to her shoulder, left knee and right wrist, overcame world No.122 Parmentier in three sets in their only previous meeting in Bogota seven years ago.
The Slovenian is also seeking the third title of her career after twice winning on the clay courts of Bastad, Sweden.
