Is Lady Gaga jealous of boyfriend Taylor Kinney and his growing friendship with Cameron Diaz, the model-actor's co-star in The Other Woman?
Despite putting on a united front with her beau in New York Monday, Gaga failed to conceal a somber expression, according to the Daily Mail (UK).
Gaga and Kinney, who have been dating for the past two years now, have reportedly hit a rough patch over his blossoming relationship with Diaz.
Says a source: "Cameron and Taylor have clicked on set and are getting on really well. They've been hanging out and the news has reached Gaga's camp."
"It's been a stressful time for Gaga with this on her plate."
Diaz, 40, has reportedly been spending lots of time with Kinney, 31, including trips to cafes and restaurants during breaks in filming of the movie.
Taylor even reportedly introduced the star to his family.
The source added: "Taylor has the perfect excuse for going for days out with Cameron as they're workmates, but they're not just being close at work."
"Cameron and Taylor have been seen in cafes and went out for dinner together. They were joined at the hip at a drinks party for Kate Upton's birthday."
Gaga, 27, is recovering from hip surgery after an injury forced her to cancel dates of her Born This Way Ball tour earlier this year, making it even tougher.
Is Diaz The Other Woman in more ways than one?
As such, she hatches a revenge plot with his wife.