Berkley's perfromance might actually be decent when you consider
That what happens to her character in the story is essentially what happened to her IRL
Nomi and Elizabeth are both young naive and inexperienced, not really knowing how to play the field of showbiz in particular, and as a result Elizabeth gives this very angry and violent performance, which seems true to Nomi's self-destructive and thrashing behavior. Nomi like Elizabeth is manipulated into acting this exaggerated way by her Vegas peers as the film's older, seasoned actors, writer and the director lead her on in her performance choices.
By all means this is not a consistently or always effectively nuanced performance, but it does the job and it seems to keep with the tone of the film and the particular kind of story they wanted tell and it's accompanying delivery from all other production aspects outside of her performance. Not exactly sure why people are so virulent. Sure it's not "authentic" or "realistic" but it doesn't want to be, and I honestly can think of dozens of other films that are even more unrealistic that no one seems to criticize.