Selena Gomez is left fuming after Justin Bieber becomes BFF’s with her ex Nick Jonas, how did he not think that would be awkward?

Selena Gomez and Justin Bieber's relationship is reportedly once again on shaky ground.

Justin has been hanging out with Selena's ex Joe. Bad move Biebs. Copyright [Wenn]

And guess who's to blame this time around?

That's right; apparently he's messed up again.

Silly Justin.

According to reports, Selena was left furious with Justin he befriended her ex-boyfriend Nick Jonas leading to her refusing to attend his Chicago concert on Saturday.

We have to say, becoming BFF's with your recently reconciled girlfriend's ex isn't the smartest of moves.

A source close to Selena told Hollywoodlife.com: "Justin and Nick Jonas hung out all last night [Thursday] Selena was crying about it.

"He wouldn't even return her calls when she found out and called him up."

To add insult to injury, Justin tweeted Friday about his day in the recording studio.

Selena wasn't exactly impressed with Justin's choice of new friend. [Copyright Wenn]

He wrote: "In the studio tonight working on the acoustic album...had some solid ping pong matches but... still #pingpongchampion"

Fair enough, however, this post was tweeted only a few hours after Nick Jonas had written this: "Just played @justinbieber in ping pong. Went to deuce both times, but he's the ping ping champion. #Igotyounexttime : )"

[Related Story: Justin Bieber opens up about 'hot girlfriend' Selena Gomez]

[Related Story: Selena Gomez calls Justin Bieber a 'jerk']

We don't think we'd be particularly impressed if we were Selena either.

Close friends to Selena Gomez now think that she should break up with the 'Boyfriend' singer as all he does is seem to upset her.

One friend reportedly said: "This is why they should break up. She keeps trying and she's heartbroken. It's not working."

Selena Gomez recently took the Justin Bieber back after he spent the evening entertaining a Victoria's Secret model.