The Hollywood star - who plays hard drinker Erin in the comedy movie alongside rumoured boyfriend Justin Long - admits she wanted the film to be as real as possible and felt it needed profanity and sex scenes to keep it true to life.
She said: "It was so great to be able to talk the way I do in real life with friends.
"I think a film about real love and life and what we go through in relationships and with our friends would be impossible to do authentically if it didn`t have any sex and bad language, because it wouldn`t be realistic."
Discussing her reason for working with Long - who she met on the set of `He`s Just Not That Into You` - on the film, Drew claims she thought of it as a "unique" opportunity.
She told the Daily Telegraph newspaper: "I thought it would be a unique experience to go to work with someone I did have a history with and I have had emotional times with and who genuinely makes me laugh and who I?m genuinely attracted to."