Trailing by two breaks in the final set, Mladenovic looked to be slipping to a surprise defeat to Kurumi Nara. However, a sloppy service game from the Japanese player left the door ajar for a Mladenovic comeback.
Two games later, she was back on level terms. With the momentum now in her favor, Mladenovic went for the jugular, breaking once more in the final game of the match to close out a 63 36 75 win.
"It feels great to be in the final," Mladenovic said. "It was another tough match, and again it was three sets. I feel really good here and I'm pretty happy with the way I'm playing since the start of the week.
"There is just one more match to go and hopefully I can get to the trophy."
After breezing past No.2 seed Olga Govortsova in the quarterfinals, Chang produced a surprisingly disjointed first set against Doi, eventually losing a one-sided tie-break.
A mid match pep talk from brother-come-coach Yao Chung, though, revitalized her game; a break in the fourth game of the second saw her level the match at one set apiece before racing away with the decider.
"At the start of the match, I was so nervous and couldn't find my rhythm," Chang said after her 67(3) 63 61 victory. "After my brother came on at one change of ends, I made some adjustments and it really turned around the match."
Chang will also be going head-to-head with Mladenovic for the doubles title on Sunday afternoon, after she teamed up with Govortsova to defeat Chan Chin-Wei and Kimiko Date-Krumm, 64 63. Earlier on, Mladenovic and partner Chan Hao-Ching had defeated Kao Shao-Yuan and Lee Hua-Chen, 61 75.