Yes, it will. =/
From CaptainEd:
(2) Let's put a ring, bracelet, or wristwatch on your arm. Put it on the arm that's nearer to the window at your left [Ed note: or some landmark that is visible in the room]. Now, your ring is closer to the window, and the mirror-ring is closer to the window. So it doesn't switch left and right. (If it did, your mirror-ring would be farther from the real window)
Maybe it is also switching the window's position, as well. =P
I don't think I would tell her this, but I've seen kids use the L method with the index finger and thumb to determine which hand is their left. Standing in front of a mirror, you would have to hold up your right hand in order for your mirror image self to see the L (which would normally indicate your left hand). Bad stuff there. Bizzarro world is likely the best answer.
Perhaps using sticks or some solid straight object to show that the reflection an object follows a straight line. Perhaps showing her how light reflects off of a mirror will help, especially if you can represent the path of reflection of an object. I hope that makes sense. If not, I'll make a video this weekend.