She will meet second-seeded Caroline Wozniacki of Denmark, who beat Russia's Elena Vesnina in the other semifinal 2-6, 6-3, 7-6 (4).
Wozniak, the tournament's No. 5 seed, won the first set and led 4-1 in the second before Petrova, ranked 10th in the world, came back to win five straight games.
"She stepped it up in the second set,'' Wozniak said. "I started backing up. Of course, my emotions got involved, but I found my composure in the third set. It feels good to beat the top seed and a top-10 player.''
Wozniak, who had 35 winners, built a 3-0 lead in the third set. She withstood the Russian's rally with a variety of well-placed shots to every area of the court.
"She played really well,'' Petrova said. "I've never seen anybody paint more lines that she did today.''
Petrova, who is coming back from a stress reaction injury to her right foot, said she's not disappointed with the loss.
"Two weeks ago they were talking about surgery so I am lucky to be able to play,'' she said. "I know when I get my feet back I'll play good tennis.''
The winner will receive $37,000 of the $220,000 purse.
Wozniak upsets Petrova in Ponte Vedra semifinals
