The move was a clever one on her part (then in hingsight, she did leave herself open). Sonya went with the blow, twisting at the last minute so that even as her fist struck its target, she wasn't so winded as a full on blow would've done (she never meant to go easy on her at all). She then twisted and deflected her arm up and over her head to feign a returning blow to Margery's side.

Only while her attention was focused on high, Sonya moved to aim a low kick just below the knee. She meant to sweep her off her feet, not break or disjoint a knee cap.