1.) Justin's song "Beauty and a Beat" : In this song he says that he needs a "Beauty and a Beat" to make his life complete. On the other hand, Selena Gomez performed a song named Beat. She compared herself to the beat that Justin needs.
2) In her song Nobody does it like you, she says " sexy kinda swag "; and we know swag is the word that is only used to describe Justin Bieber.
3) In his song "Beauty and a Beat" It is clearly 说 in Nicki Minaj's rap "Selener" 或者 simply, Selena.
4) In Justin's song She don't like the lights he says "she can't hide away 'cz the world knows who we are". He is, may be, talking about him and Selena.
If 你 know something like that, then please comment.