The 23-year-old produced her latest single I Will Never Let You Down — which she described as a "love song you can dance to" — with the legendary Scottish DJ.
Speaking to BBC Radio 1 host Nick Grimshaw, Rita laughed, saying she found it hard to concentrate with her beau in the studio.
"I was actually a bit nervous because he's never seen me in work mode," she said. "But literally just ten minutes in he was so blunt. I think it's the Scottish-ness in him, he was just like 'no' etc. and it happened so quick. It was a very good experience.
"It's about having fun and because I take everything so seriously, I'm always a bit like work, work. He's like, 'you really need to just enjoy it.' And I agree, so I'm just enjoying it right now. And I'm happy we kind of did it together. It's a nice little feeling for me, it makes it personal."
Rita and Calvin, 30, have been dating for almost a year. The couple put rumours that they had split to rest when they were spotted attending the Grammy awards together.
Rita fuelled speculation that she and Calvin were no longer an item when she posted a cryptic image on Instagram, writing, "Have you ever wondered which hurts the most: Saying something & not wishing you had not, or saying nothing and wishing you had?"