Some of them never will, because they're used to seeing themselves in a mirror with the image reversed. Try flipping the image & see it that works. ; )
its amazing how well this work.
there is a woman i have photographed a few times, and she hates having her photo taken, says she always looks a bit odd, but can never tell me exactly why.
last time i photographed her i loaded the pics straight into the laptop, picked 2 shots, flipped them both (so i had 4) and then asked her to pick which one she preferred.
she picked the flipped ones.
when i explained to her what i had done, and the reason she didn't like photos of herself, she was amazed.
was a fun little experiment....