Yes, right next to the Main Street Tattoo Parlor.
I'm kidding. I have no idea. I just can't imagine Disney encouraging the piercing of anything, though ears are fairly standard business. There are jewelry stores, though, so maybe someone will know for sure.
But, it was a fairly traumatic experience for my DD. She wanted them done so badly but she still blames me for not warning her enough about the pain (which I don't recall to be all that bad, and she got over it quickly enough, but still...). I'm not sure you wouldn't be better off doing it at home before you leave to give her time to adjust before you're actually at WDW. If it's not a great memory for her later, you might not want her to associate it with such a happy place. But hopefully your experience will be completely different, anyway.