Given the obvious height difference, it was clear who'd win, and if Magica had her classic "foof" bombs, she'd toss one and make a getaway.

She still planned on running away - but needed to do it the "least cowardly way" possible. Which, in her mind, counted as this -

"Who are raising children these days to make them so violent." She casually walked to then around Mal, as if making it look like she was going to merely walk off. "Honestly... this makes me glad I had no brats of my own!"

And so, her "plan" kicked in - which was just quickly raising her foot and using the heel part of her high-heel shoe to kick Mal in the shin.