The Hungarian Szavay fell flat during key points in the second set, having earlier beaten seventh-seeded Iveta Benesova of the Czech Republic 6-2, 6-2 in a rain-delayed quarterfinal match at the Bad Gastein, Austria, event.
"I feel very happy," said Parmentier, whose win over the player ranked No. 14 in the world was the first of her career against a top 20 opponent. "It has been a good week for me and I hope (Sunday) will make it a perfect week."
In Saturday's other semifinal, a battle of non-seeds, Czech Lucie Hradecka trounced Mariya Koryttseva of Ukraine 6-3, 6-2.
The winner of Sunday's Parmentier-Hradecka title match will collect a first prize check of $28,000.