Selena Gomez: Done with Justin Bieber!

With Justin Bieber smoking weed making all the headlines this week, another major development in this singer's life has practically gone unnoticed:

He and Selena Gomez have broken up again. And sources tell Us Weekly this time, the split will stick.

• 
• 

Bieber and Gomez cut their vacation short in Puerta Vallarta, Mexico around New Year's because they had a "huge fight," an insider tells this tabloid, adding ominously:

"Selena won't forgive him."

It's unclear what caused the argument, but Selena spent December 31 with friends in Los Angeles, while Bieber rang in 2013 with Lil Twist, reportedly flirting with girls and, as we all know, smoking some pot a couple days later.

But Justin is "really down about the breakup," a source admits, though that doesn't mean he'll get another chance:

"Selena is done with him."

Sad stuff. But at least Bieber knows how to make his mood to from low to high... if you know what we mean!