The Australian top seed was a 6-2 6-3 winner against seventh-seeded South African Chanelle Scheepers.
She will play China's Zheng Jie in the semi-finals after the unseeded former Wimbledon semi-finalist secured a fine win over Czech player Petra Cetkovska.
Cetkovska ran through the opening set without dropping a game, allowing Zheng just eight points, but the match turned around.
It was soon level and finely poised when the players went off at 3-2 to Zheng, on serve in the third set, due to a downpour.
Zheng broke immediately on the resumption and had match point against Cetkovska's serve at 5-2. Cetkovska staved off the immediate threat but Zheng then held serve comfortably to reach the semi-finals with a 0-6 7-5 6-3 success.
The other semi-final will see second seed Marion Bartoli take on third seed Angelique Kerber.
France's Bartoli was ruthless against the last Japanese player remaining in the tournament, crushing home hopes with a 6-2 6-1 victory over sixth seed Ayumi Morita.
German Kerber also triumphed in straight sets, 6-3 6-4 against Thailand's Tamarine Tanasugarn.
The semi-finals had been scheduled to follow the completion of the quarter-finals, but the wet weather in Osaka prevented them starting, meaning both last-four matches and the final are due to be played on Sunday.