New York, NY -- It's gotten to the point where Selena Gomez can joke about her breakup with Justin Bieber. Gomez was a guest on "Late Show With David Letterman." Letterman told her that when Bieber was on his show he said something that made Bieber cry. And Gomez shot back, "Well, that makes two of us." Letterman was so impressed with her comeback he held out his hand for a fist-bump. Asked how she's doing since the split, Gomez said she's "so good."