Most reviewers are taking this movie too literally. Of course the plot is ridiculous and the characters are simpleton and/or abusive stereotypes. The story is of the failed-fallen women genre but updated to the 1980's and it's full of too-recognizable motifs and characters. Enjoy it for the screen candy (sour/sweet) it is.
Dolly Parton wrote a terrific catchy song, and E.L.Doctorow wrote a 3 1/2 page story that reads like a tightly-constructed fable . . . that there are multiple complications in the life of a young/maturing, sexy-beyond-her-maturity, girl/women. It is a fantastical tale, yes.
And Dan Ireland, Jessica Chastain and an underrated cast bring this fable to life. It's not particularly realistic nor pleasant, but Ms Chastain is brilliant (again), and yes quite beautiful too. Take it for what it is, and watch one of two greatest actresses of our era from Sacramento, CA light up your screen!