Cornet, 18, had no answer for Jankovic's relentlessly consistent groundstrokes as the errors piled up, reducing her to tears at the changeover when she was trailing 1-4 in the second.
The precision serve that had helped Cornet defeat two Russian top tenners, fifth-ranked Svetlana Kuznetsova and eighth-ranked Anna Chakvetadze, deserted her on Sunday.
"I'm very disappointed, but next time it'll be better," said Cornet, who dropped only one set -- to Chakvetadze on Saturday -- on her way to the final.
"I started to be very tired. ... I couldn't do what I wanted to do on the court," said Cornet, whose run here will see her WTA ranking rise from 34 to about 22.
Jankovic, although she hardly showed it, said she was "very nervous" on the court.
The 23-year-old Serbian champion, ranked fourth in the world, had work on her right shoulder towards the end of the match.
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