"brutal violence against a particularly vulnerable woman who has little bearing on the plot."
It's not like they just stood on stage and beat the woman to death for 10 minutes. It was actually extremely effective in making the audience think and realize that this show wasn't just about the emcee going around smacking womens asses all night. And she was in the show as more than a KitKat dancer. I'm not familiar with other versions as I have only seen the movie, but coming from the perspective of someone seeing the show for the first time, it didn't seem like she was just this random woman getting beaten up at the end. I continually saw her from the first number (she stood out from the other girls), and she had that number where she was in a gorilla suit, etc. I'm not sure if it's because I noticed right away how different she looked and just had a feeling that she would be involved more in the plot than just one of the girls.