Now, I'm not 100% certian here, but I think by the in-game reply of "Because I think calling someone a <blue text> is PRET-ty harsh!" is the type of reply that you get immedatly from a character when they ask you to enter in some kind of catch phrase and you enter in the vulgarity in response.
It is my belief that this little girl did not get this from going online, visiting someone else's town or someone else playing her copy at some other time. I'd almost bet that the little girl keyed in the text, saw that response who showed it to her mom who throught her little girl could never do wrong and went crazy at Nintendo. All this happened in one sitting.
Stupid f'ing cow.