Taylor Swift was reportedly furious with Calvin Harris after he opted against accompanying her to this year's Grammy Awards.
A source explained to The Sun newspaper: "Taylor was furious and hated the way he never wanted to attend award shows and big music industry events with her.
"It was a Sunday night in LA and she felt he could have slipped away for a couple of hours to be with her."
Meanwhile, sources close to Calvin have also suggested Taylor was moving in on her new boyfriend Tom Hiddleston while the DJ was in hospital following a car crash.
In May, Calvin was rushed to a medical centre in Los Angeles to receive treatment for injuries he sustained in the crash.
The singer subsequently flew from her home in Nashville to visit Calvin the next day, but she ultimately spent just one day by his side, despite the severity of his injuries.
A source said: "Taylor's true colours are coming out. The truth is she met Tom in February and things are moving very quickly. She had vacated her relationship with Calvin way before she let on."
Since Taylor and Tom's romance has gone public, the celebrity duo have been widely accused of orchestrating a publicity stunt to further their own careers.
But earlier this week, Tom denied those suggestions.
The 'Thor' actor said: "The truth is that Taylor Swift and I are together and we're very happy."