Like the girls who smile in tampon commercials, this picture reeks of insincerity.
As someone who knows a thing or two about women forcing a smile, I can confirm that something is amiss here. The amount of lip gloss necessary to keep the Joker-calibre smile glistening would be absurd.
Found by Omegaresnovae who ran across this sitting on top of a cheese display when she was shopping at a local grocery chain.