The Frenchwoman broke Dementieva twice in the third set, winning the opening game on a forehand error from Dementieva before increasing her lead to 4-1 after the Russian sent a backhand wide.
Dementieva saved a match point at 5-2 to erase a break, but Mauresmo converted her second match point with a service winner for the former top-ranked player's first title since Antwerp, Belgium, in February 2007.
"The feeling you have when you conclude a tournament with the title is different than a good week with a defeat,'' Mauresmo said. "It's a special feeling. It gives you an extraordinary confidence.''
The two players traded breaks in the first set until the fourth-ranked Dementieva held her serve to take a 4-2 lead, but Mauresmo managed another break to draw level at 5-5. In the tiebreaker, Dementieva slammed a forehand winner on the line at 5-5 to get the first set point, but she wasted it with a backhand pass that sailed wide.
A forehand error from Dementieva at 7-7 gave Mauresmo her second set point, which she converted when Dementieva sent a forehand return into the net.
Dementieva came back in the second, breaking Mauresmo for a 4-2 lead and securing the set when Mauresmo made two consecutive double faults.
"Amelie really picked up her game and played at her best this week,'' Dementieva said. "I'm very happy for her. She had such a tough time to go through, with all the injuries, and she was trying so hard to come back to the level she used to play.''
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