In the film, directed by Mann's husband Judd Apatow, her character runs a boutique store and stumbles across her colleague, played by new-mum Fox, trying on a push-up bra.
During the scene, Mann grabs at Fox's chest and admits she found the whole situation uncomfortable because she felt so protective of her younger co-star.
Mann tells Yahoo! Movies, "I feel very protective of younger actresses because it was so hard for me in the business. I wanted to get it over (with) as quickly as possible, because I knew it was uncomfortable for her, probably - or maybe not.
"But just in that situation I knew there were a lot of dirty boys around having weird, gross fantasies. And so I wanted to get her shirt back on as quickly as possible."
Mann wasn't the only one who felt awkward about the scene - Apatow insists he only shot the minimum amount of takes.
He adds, "I get so uncomfortable with even partial nudity in movies. I'll do one or two takes, and feel weird."