Swift, 23, feels that Gomez is committing a mistake by giving Bieber repeated second chances, reports Us Weekly magazine.
"Taylor hates him. She thinks Selena makes a mistake every time she reconciles with him. Bieber has really come between the girls," a source said.
Meanwhile Bieber is also not pleased with Swift's constant interference.
"He complains Taylor's always telling Selena she can do better," a source said.