Yes, her ears are pierced, and those are real pierced earrings that she's wearing.
She got her ears pierced back in January this year, along with her big sister, Melissa. Actually, its the third time Jennifer has had her ears pierced, as she had them done for a movie a few years back and then let them heal up again, then had them re-pierced in 2006 for the earrings she wore to the Oscars that year, but then let them heal up again. In the picture Du posted, the earrings she's wearing are the ones which seem to be her favorites, and Du can see that they're not clip-ons. And if Du look at the current candid pictures of her where she's not wearing earrings, like the one below, Du can clearly see the holes in her earlobes.
So the answer to your Frage is yes - Jennifer really does have her ears pierced now, although she doesn't always wear earrings.