The reigning Wimbledon and U.S. Open titlist extended her lifetime mark at Crandon Park to 59-7 with the victory -- tying Steffi Graf for the most career wins in Key Biscayne.
She'll next face fourth-seeded defending champion Radwanska, who scored a 4-6, 6-4, 6-2 quarterfinal decision over 30th-seeded Kirsten Flipkens of Belgium.
The Pole stayed hot with her 23rd win in 27 matches this year.
Third-seeded former world No. 1 Maria Sharapova will meet eighth-seeded Sara Errani of Italy and No. 15 Roberta Vinci, also of Italy, faces off against 22nd-seeded Serbian Jelena Jankovic in Wednesday's quarterfinal match-ups.