Singer disappointed over Justin Bieber/ Kourtney Kardashian fling?

Selena Gomez, 23, has reacted at the alleged affair with her ex, Justin Bieber, 21, and Kourtney Kardashian, 37, and reports say she's furious.

According to Hollywod Life, the singer was  'devastated’ when the news broke that Justin has been having a 4-month fling with Kourtney that overlapped with when he serenaded her by singing 'My Girl' in the lobby of The Montage Hotel on November 20! That’s when she flipped out and sent him very angry text messages!

READ MORE: Model recounts threesome with Justin Bieber

In Touch magazine claims Gomez flipped out on Kourtney and reportedly called her up. Then she sent Justin a slew of angry texts.

"Selena texting Justin and expressed how used she felt, since they’d just hooked up around the time of the American Music Awards. But his response was, ‘You know how this business works,’ meaning he did it for the publicity.'" Yikes, we really hope this isn’t true but this is low!

READ MORE: Kourtney Kardashian spotted with Diddy's son amid rumors of dating Justin Bieber

“Selena thinks it’s bizarrely incestuous and doesn’t understand why Kourtney would go there after her sisters," an insider also tells the magazine. “Selena’s telling people she think it's sick for Justin to be hooking up with so many people in the same family."

But Kourtney’s family also reportedly thinks it’s gross too! “[They] think it’s crazy that she hooked up with their ex. earlier this year. She feels betrayed," the mag claims.