I have no argument against that. Not that I'm totally innocent of opera, and I have on occasion seen black-and-white TV takes of some of her singing.
Needless to say, she was hardly the only "virtuoso" to be temperamental. I sometimes wonder if it's a case of fame going to their heads, though. Just because one is good doesn't mean he/she is God's right hand. Horowitz, Heifitz, and yes, Fox, had their idiosyncracies. And there seems to be something of a trait among "artists" to be known for their temperaments. Writers and painters, etc. count among those.
Somehow, some seem to escape the sterotype. Isaac Stern seems to have been pretty decent, as is Perlman, and some others.
There for some time, it seemed to me that record companies went fighting over every twelve-year-old oriental girl who picked up a violin. Wonder how they are doing by now.