The pop star was hanging out with McGregor and Lewis Hamilton at the British Fashion Awards and tweeted a picture captioned ‘date night’.
It fuelled criticism from McGregor fans due to his relationship with Dee Devlin.
And McGregor’s SBG team-mate Artem Lobov has now tweeted: “Sorry Rita, Burgers are nice but not when a man has steak at home.”
McGregor had his first child – Conor Jnr – with Dee earlier this year and has been with her for nine years.
And fans were quick to get at Rita for her post.
One tweeted: “You’ve got a fine Irish steak at home mate. No need to ruin it with a McDonald’s.”
“That’s lovely for his partner and mother of his child, have a bit of respect maybe?,” fumed another.
While a third added: “Man feel bad for Dee seeing these pictures and seeing him liking all these lasses posts on Instagram, followed Conor for so long and he’s seemed to of changed so much, money got to his head.”
McGregor has been out of action since his showdown with Floyd Mayweather in Las Vegas.
He is expected to return to the Octagon next year with UFC stars lining up for a shot at him.
But Mayweather has claimed he had to carry McGregor through the boxing bout to make it look good.
“Everybody tried to protest the Mayweather-McGregor fight, right?” Mayweather said, via FightHype.
“But I’m going to tell you all the truth. You know I carried McGregor. You know I made it look good for y’all.”