Why Are Selena Gomez And Justin Bieber Fighting Over Nick Jonas?

Just when it seemed like Selena Gomez and Justin Bieber's relationship was on the mend, it looks like things are going south again! Earlier this week, Selena posted a homemade video dancing to BFF Taylor Swift's single "I Knew You Were Trouble" on Twitter, prompting talk of a Bieber diss. Now it's Justin's turn to spark some chatter after Sel's on-and-off-again boyfriend had a highly-publicized hangout with her ex, Nick Jonas. 

A source close to Selena revealed, “Justin and Nick Jonas hung out all last night [Dec. 13]. Selena was crying about it. He wouldn’t even return her calls when she found out and called him up.”

The Biebs and the youngest Jo Bro announced to the Twitter world that they'd been hanging out, posting:

Yikes! This doesn't sound good for the future of Juslena! Sel has made it very clear that she and Nick's split was a devastating one for her and Justin spending time with him only adds salt to Sel's unhealed wounds. 

Your current boyfriend hanging out with your ex: friendly mature move or a big no-no?