In the new NBC sitcom, Kelly and Nick play a married couple but the pair have been warned to keep their romance strictly on screen.
"I can't date him," the model revealed to The Sun. "We've been told we're not allowed to!"
Told to keep their relationship purely platonic when in front of the cameras, Kelly admitted it would be "awkward for everyone" if she and Nick did get together.
Although it seems being warned away from each other has only spurred the pair on more when it comes to filming!
The 35-year-old added: "We keep it all onscreen, so when we're kissing we really go for it... there's a lot of pent-up sexual tension."
Suggesting she would be interested if a ban wasn't in place, Kelly then said: "[Nick's] a lovely guy. In my dreams I'd like to imagine he would date me."
Kelly first met What I Like About You star Nick last year after landing a role on One Big Happy.
On the show - produced by Ellen DeGeneres - she plays a British woman named Prudence who Nick's character falls in love with and marries. But things get complicated as he and his lesbian best friend (Elisha Cuthbert) are expecting a baby together.
Last week, Kelly made her NBC debut as One Big Happy aired for the first time in the US. And the starlet gave fans more than they bargained for as she appeared completely naked during the episode - just like the trailer had teased a few months back!
Following the episode airing, Kelly celebrated her arrival on US TV with her co-stars and 1000 magnums of champagne - we're not kidding!
As a congratulatory treat, the British model revealed Ellen DeGeneres had sent the cast 1000 bottles of bubbly and 59 butlers in the buff.
Well, that's definitely one way to celebrate, right?!
One Big Happy airs on Tuesday nights on NBC.
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Watch the trailer for One Big Happy here: