Michele and Kutcher play one of the couples in the Garry Marshall holiday movie, which also stars Zac Efron, Jessica Biel, Hilary Swank, Ludacris, Halle Berry, Robert De Niro and Katherine Heigl.
When asked if she was curious about the casting for her love interest, the Glee actress told New York Magazine: "I was! Garry was like, 'Who do you think is cute? What guys do you like? Who do you want to be in this movie with you?' And I was like, 'I don't know, I've never been asked before!'
"I didn't mention Ashton's name just because, I gotta say, I kinda felt like he was a little out of my league. You know, this guy's like, the hottest guy, and then when they called and said that Ashton was doing it, I was really freaked out.
"I thought I should have picked someone else and said, 'You have to use this person!' so I wouldn't have been nervous. But I'm so glad, because he challenged me, and it was a really great pairing, I think."
Kutcher recently split with Demi Moore, who filed for divorce from the actor, while Michele ended her relationship with boyfriend Theo Stockman.
Michelle also addressed the Les Misérables casting rumours, remarking on the change of the industry.
"I was just talking to my publicist yesterday that it didn't used to be like this in the business; I've been up for a lot of movies before that I really wanted to get, but now, people know a lot more than they used to and it's all out there," she added.
"Like, I remember when my co-star Dianna [Agron] was up for Spider-Man that the news was online, and I felt really uncomfortable for her. I mean, yeah, it's super cool that you're in consideration, but it's also a really private thing, and then if you don't get it...
"But I'm happy to be considered, and I'm happy to be in the realm of the other girls who are being considered because that's the coolest thing for me. When I heard the other people they were considering, I was like, 'Wow, this is awesome'. I became, like, a fan dork girl."
New Year's Eve opens in theatres on December 8 in the UK and December 9 in the US.
Watch the trailer for New Year's Eve below: