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Selena Gomez is getting in some low blows against Justin Bieber  and doesn't have any regrets.

The Spring Breakers star gleefully told David Letterman on March 18 that she has made the Biebs cry, and apparently she's glad she said that. 

“Selena loved dissing Justin during Letterman,” a source tells Hollywood Life

“She feels great these days, because she looks hot, and has a hot new movie Spring Breakers out, and she has had great success with the The Wizards Return," the source adds. "Everyone is rallying around her.” 

Meanwhile, her ex isn’t doing so well lately.

“Justin is turning into Lindsay Lohan, what with all the partying and him canceling his concert," the source says. "She feels that he has become less popular, and she’s just turning into a bad bitch with worldwide fans."

"She feels like she is on top of the world because she is," the insider continues.

Wow! We're loving this feisty new Selena. But a note to self: Never get on her bad side.

Source: Hollywood Life