Well, the issue is that the character doesn't use magic. While a wish started things, Miss Fine is just a manipulator. So how would anyone who saw them not notice something strange was going on?
You can't control everyone's mind...well, you could, but that seems out of scope. So the sole reason for changes in physical appearance is because other people would notice something strange.
Or maybe that is the point. That people do comment but they just don't believe them. Or, in the world Jon wished up, people are used to such things.
