In a decade-long rivalry, Dementieva earned her easiest win over Mauresmo, only her sixth in 14 matchups.
The Russian won the last eight games, and limited the fifth-seeded Frenchwoman to only nine points in the second set.
Next up for the Olympic champion, chasing her third title of the year, will be eighth-seeded Sorana Cirstea of Romania.
Cirstea, the winner at Tashkent this month, upset third-seeded Daniela Hantuchova of Slovakia, last year's runner-up, 7-6 (2), 6-2.
The other semifinal on Saturday features a first-time meeting between fourth-seeded Caroline Wozniacki of Denmark against sixth-seeded Li Na of China.
Wozniacki beat seventh-seeded Anabel Medina Garrigues of Spain 6-1, 7-6 (7), and Li outlasted Iveta Benesova of the Czech Republic 6-4, 4-6, 6-2.
Dementieva, Wozniacki, Li, Cirstea reach quarters
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