Selena Gomez's rumored on-again, off-again relationship with Justin Bieber is causing a rift between her and best friend Taylor Swift, sources told Us Weekly.

Swift, 23, reportedly cannot stand the back and forth romance her friend is in with the Heartbreaker singer. The couple began dating in 2011 and reports of their breakup surfaced toward the end of 2012. In July of this year, Swift called 21-year-old Gomez "the closest thing I've ever had to a sister," but she does not share similar sentiments toward Bieber, 19.

"Taylor hates him. She thinks Selena makes a mistake every time she reconciles with him," a source told the magazine. "Bieber has really come between the girls."

The feelings are reportedly mutual, with a Bieber source telling the publication, "he complains Taylor's always telling Selena she can do better."


When press asked Swift about Bieber at the Billboard Music Awards in May, the I Knew You Were Trouble singer declined to comment, instead saying, "Can we have another question?" Later that night Gomez and Bieber were caught kissing and hugging backstage, and while watching the action take place, Swift was seen sticking out her tongue in disgust.

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Swift did not attend Gomez's 21st birthday bash with Bieber and her friends in Malibu on Saturday, July 27. An eyewitness said Bieber arrived at the celebration with a single red rose as a present for Gomez. The former couple was also spotted together at a Fourth of July party.

Though they may feel differently toward Bieber, a rep for Swift reassured fans that the female singers maintain their friendship, saying, "Selena and Taylor are great friends who talk almost daily."

Both Swift and Gomez are currently on tour promoting their latest albums.