Parmentier, who last won a title at Bad Gastein, Austria in 2008, needed two hours 13 minutes to defeat a determined Hercog in the claycourt tournament.
Slovenia’s Hercog fired 26 winners to Parmentier’s seven but the world number 75 also made 34 unforced errors to allow her opponent to make it three wins in three career finals.
“This is just awesome. It was a perfect week,” world number 122 Parmentier said. “I didn’t expect to be here today and to have the trophy.”
Hercog had beaten Parmentier in three sets in their only previous meeting in Bogota in 2011.
The 27-year-old did well to level the match at one set apiece after losing the first set but had no answers to Parmentier’s powerful play late in the decider.
“I’m a bit disappointed today but we did a great job this week,” Hercog said.
