The seventh-seeded Romanian had six aces and broke for a 2-0 lead in the second set. She fought off two break points in the final game before closing out the match with two forehand winners to win the first of four career finals.
Petkovic, a German wild card, was in her first final in more than 20 months after injuries and was seeking her third title. A former top-10 player, Petkovic is on the comeback trail.
"Simona played incredibly and I was a little tired," Petkovic said.
"Still, I had a good week."