The actress stars alongside Isla Fisher and James Marsden in the new movie, about a bachelorette party which spirals out of control.
In one saucy scene, Dunst's character has sex in the bathroom of a strip club, and she has warned her dad to stay away from the movie.
She tells E! News, "I can't do that to him. I didn't even tell him there was an LA premiere. And I was like, 'Yeah, dad - don't even try getting it on iTunes because you will not like this movie. You're a prude. You will hate it. I know you!'"