She said: "I swear a lot in My Best Friend's Girl. But I actually talk like that. It was fun to swear in a movie.
"In real life, I can't hold a conversation without swearing, unless I have a script."
"The actress - more famed for her roles in romantic comedies - has previously admitted she loved the chance to experience playing a sexually aggressive character in My Best Friend's Girl.
She said: "I got to say and do certain things that most people say to each other in normal, everyday life. I got a little taste of what those Sex and the City girls were up to for so long, which was fun."
However, Kate - who is divorced from Black Crowes singer Chris Robinson - tries to be more careful with her language in front of four-year-old son Ryder.
She added: "Now that I have a son, I don't swear as often on a day-to-day basis. But boy, yeah, I can throw out some bad words every once in a while."
