The British actress - who plays Winnie, the estranged daughter of Michael Douglas's character Gordon Gekko in the sequel - said she wanted to be more than "just an accessory to the plot."
She explained: "The challenge was to try and make the girlfriend role in a Hollywood film effective and not just redundant. I think a lot of the time, through no fault of the actress, the girlfriend can be marginalised and just an accessory to the plot. I thought there was something to play there, and more than just the girlfriend."
The 25-year-old star also admitted that she relished being "intimidated" by Hollywood heavyweights Michael Douglas and Oliver Stone on the set of the movie.
She said: "I kind of wanted to be in a Big Boy's film and be intimidated. There were other roles going on in England that I was kind of involved in, but there was nothing going on that I would wake up in the morning and go, "oh, s**t, how am I going to do this? That was sort of exciting. I did want to be one of the few Women in a big, masculine film. And it was fun.
Although she played Michael's daughter in the film, Carey revealed the pair didn't become close off camera because it would have ruined their scenes together.
Speaking at the Toronto Film Festival, she said: "I loved working with all of them, including Michael. We sort of kept a distance from each other. We didn't get all cuddly off set, we were quite removed, so when we played those scenes, I didn't really know him, and that was appropriate because I didn't know him in the film."