how i always wondered that.

I think the best model for it is how her foot claws work in her movie version; rather than the claws being stowed in her feet, they fit between the two bones of her lower leg (much the same as the claws in her hands fit between the bones of her forearms). Extending the claw requires her to point her foot, (watch Keen's performance in Logan: Whenever the foot claw comes out you can see her give her foot a slight flick to allow the claw to extend) though once it's extended she can plant her foot as normal. The comics just don't show this detail because of the lack of motion on-panel.

@ambaryerno: then how dose she walk when there in her body i assume they go in her leg maybe.