Selena Gomez Cheating on Justin Bieber For Cory Monteith?

GLEE start Cory Monteith arrived at Nickelodeon’s 24th Annual Kid’s Choice Awards with Justin Bieber’s Girlfriend Selena Gomez on April 02,2011 in Los Angeles,CA.
Both Selena Gomez and Cory Monteith seen very happy at that event..
Where is Justin Bieber?? Selena Gomez doesn’t seems to miss him at all..