After dropping the first set 6-7 (8-10), the Serbian maintained her composure and took the next two 7-5, 6-2.
She continued her recent winning ways despite a broken toe nail on her left foot.
"I am so excited to be back in the final and playing my best tennis," Jankovic told the BBC.
She will face unseeded Nadia Petrova of Russia in Sunday's title match.
Jankovic improved to 5-3 lifetime against the American great, including a win in a quarterfinal in Rome this season, and, overall, has won five of their last six meetings.
Petrova beat Belarusian Victoria Azarenka 6-4, 6-4, in Saturday's other semifinal.
Sunday's Jankovic-Petrova winner will earn a $100,000 first-place check.
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