I think she is only angry because she was finding the latin dances difficult and when she finally improves and gets it right she gets voted out !.
If it was one of the other earlier latin dances ( esp the one that she messed up in the beginning (Paso ?) ), then I don't think she would have minded too much at being voted out on that dance. I think it is a shame as I really saw the improvement on the Cha Cha and liked the choreography.
She must be feeling even worse now John has quit !
Personally I was gutted that Cherie was voted out and would of liked her to at least of got to the semi final, but what's done is done, a la Gabby Logan, Kate Garraway and Christopher Parker, however I don't think John should of quit, all those phone votes that would have gone to charity gone now.
All the judges needed to do is stop bullying him, therefore reduce the audience sympathy voting.