Cameron and Kate star alongside Leslie Mann in the new Hollywood rom-com, which sees the trio frolicking about in swimsuits on the beach in one scene.
The blonde actress added: "I wasn't like, 'Oh my god, I am going to be in a bikini and Kate is going to be in a bikini and what is everyone going to think of me'.
"In fact when we did that scene I was barely working out."
Kate confirmed it was her "birthday week so we were definitely not working out", adding: "Bathing suits are a part of life.
"When people go to the beach, that's what they wear."
Talking more generally about the movie, which sees the three women exacting revenge on the man they're all involved with, Cameron said: "I like also the story of telling women that they don't have to; they don't have to stay in a shit marriage with somebody that doesn't appreciate them.
"They don't have to date a man who is unavailable to them; they can also go and be free and not stick with somebody who isn't honest with them. I really love putting that message out there."
MORE! See what The Other Woman has in store in the trailer below...