Dirty Girl is well named. That girl certainly has an uncouth attitude. I liked her right away. The scenario doesn't bring much of anything new except that liberating sensation you get when you watch a promiscuous girl be the star of a film without an undertone of she-should-change-her-ways. Everything is in the rendering, particularly the acting.
The 80s/redneck campy attitude can get on your last nerve by the end because it's heavily plastering everything, and the end itself is kind of overdone, but that's on purpose to give it a special feel. I could have lived without it.
You hate the guy's father, find his mother very sweet, and finally can't help but understand the girl's real father.
If you want to watch a different comedy, with a touch of drama, it could be for you. It's entertaining.