Most of the female characters I've seen hold their katana to the side with their other hand on their hip when their idle; but I've seen a few that hold their katana in front of them with their other hand on the blade of the katana.

Is the idle stance just random? I probably should have provided pictures instead of vague descriptions but I'm lazy.

EDIT: Okay, found it. Apparently the Battle Princess shoes changes your sword idle stance. So if you want your girl to hold her sword more demurely, put those on.