Huh, okay, I've found a Carole Nelson Douglas interview where she say the contradiction was that Doyle called her both a contralto and a prima donna, and there were no contralto prima donnas*, so she made her a soprano (instead of just making her so awesome that she was a prima donna anyway.)

I'm not sure what I think of that - I'd rather have made the prima donna bit the incorrect one, because Irene being contralto makes so much sense, and it seems more likely that an English paper would have exaggerated her position than got her voice wrong - but at least she had a reason?

*quick late-night research is telling me that not all prima donnas are soprano, just nearly all. So. Maybe.