"Taylor hates him," tattles a source. "She thinks Selena makes a mistake every time she reconciles with him. Bieber has really come between the girls."
Of course, Swifty's feelings about Jelena's on-off status are hardly a secret, considering the gif-tastic face she made over their backstage kiss at the Billboard Music Awards in May.
As for Bieber, "He complains Taylor's always telling Selena she can do better," alleges an insider. (Hey, sometimes the truth hurts, buddy.)
Swift, 23, who last month called Gomez "the closest thing I've ever had to a sister," denies there's been a falling-out.
"Selena and Taylor are great friends who talk almost daily," says her rep.
Gomez, 21, also drove home their chummy status during a sit-down this week with the ladies of "The Talk," calling Swift her "best friend" and "one of the most incredible, sweet people ever."
She even shared an anecdote from her recent getaway to Taylor's new Rhode Island estate: "She picked me up from the airport. And my song came on [the radio] and we freaked out, and then her song came on and we freaked out. We were just, like, dancing in the car. … That's why we're friends."
Click on for more photos of Taylor and Selena palling around …