The `Baby` singer had a huge bust up with his girlfriend on the day before New Year`s Eve (30.12.12), prompting her to fly home to the US from the resort of Puerta Vallarta in Mexico. Multiple sources have since confirmed to Us Weekly the on/off couple have now split for good. A source said: "He`s been really down about the break-up." Selena spent New Year at a house party with her friends, while Justin partied at Los Angeles club Couture with rapper Lil` Twist. The 18-year-old star has since been pictured smoking marijuana, with some blaming Justin`s rapper friend as a bad influence. The incident was the final nail in the coffin of the romance for Selena who was unimpressed by his actions. Another source added: "Selena is done with him." The `Monte Carlo` actress tweeted on January 2: "New beginnings. Fresh start. I love you all :) (sic)" Justin appears to have taken the split harder, and was reported to be desperately calling his ex since she called time on their relationship. Another source said: "Justin`s devastated and pathetic right now. He`s calling her 100 times a day and she`s not picking up."