Carlotta is writen as a horrid character. She tells rumors and plans schemes to eliminate christine as her competition. I think what is often overlooked is that Carlotta is one of the so many victims of the book. From what is written you can tell that Carlotta was extremely talented as an opera singer as the book mentions how perfect an instrument her voice was. She had the misfortune to be ill and be replaced by someone far more loved and adored than herself, that in itself is enough to make anyone mad, take a day of sick and your job isnt waiting for you when you get back. Not only was she replaced in a perfectly unfortunate manner she was sabotaged when trying to get back to the top.
She was one of the victims of the oh so lovely Erik (<3), who doesnt care who he has to stand on to take the love of his life to such heights. True Carlotta was well simply a bitch towards Christine she just wanted to have her life back, wanted her fickle fans and power back. What she did was wrong, trying to destroy young and tallented Christine (and im sure she would have succeded without Erik on Christine's side) in sabotaging her preformance and rumoring of what Christine had apparently done to her among all the others (but we all know the story inside out so details are simply not needed) but i do understand her point of view, she wasn't going down without a fight but little did she know how powerful and passionate a man with whom she did fight. Although she was simply mean i think she needs credit where it is due, she was brave. Even after threats of misforunes worse than death if she did preform she still kept trying, she didnt run and hide, she went out there and put her life on the line to get her carrer back, that true dedication to your work.