Look at the close-up in panel 2. It's probably because of the medicine that Murasa's not liking the soup, and not because it's too hot and/or spicy.
That's not medicine; it's more likely dried ginger. (Well, okay, that's medicine of a sort, but not like pharmaceutical pills or anything.) The hatching effect on Murasa's tongue in panel 4, in conjunction with the steam coming from the bowl in panel 3, implies the soup scalded her.