In prim cocktail dress and pumps, Bliss appears to be in drag. She's more herself in thrift-shop dresses and combat boots. Obviously, the pageant world is too restrained for her. It doesn't permit a full range of social and physical expression.
When Bliss sees brazen skater-grrls - hair flying and fishnets snagged - roll into a thrift shop, she finds her spiritual sisters. For her, these hellions on wheels nicknamed Iron Maven (Juliette Lewis), Maggie Mayhem (Kristen Wiig), and Smashley Simpson (Barrymore herself) fearlessly exhibit the free-spirited physicality Bliss hides under taffeta.
The derby daredevils don't care that the men in the audience come for the girl-on-girl action. The girls are there because skating allows them to compete and, yeah, be physically aggressive in the context of contact sport.
More intimately than most in Hollywood, Barrymore knows how few female types there are on screen. Beyond the good girl and the bad girl (movie versions of the madonna and the whore), there are square pegs. Barrymore puts faces and gives backstories to these nonconformists trying to define themselves before others define them. The chief appeal of the film is to watch Bliss, misfit among angelic pageant girls, emerge as derby devil Babe Ruthless - sensitive, combative, girly, butch, timid, and fearless - whisking conflicting femininities into one tasty serving.