She barely has a  octave range Its not impossible to have an  octave range which is currently the guiness world record for largest vocal range held by Georgia Brown GG is her range but Ive only heard G since her G is actually able to be heard and sounds more like a B or B Nicola Sedda actually has the largest vocal range that I know of which I only remember his highest as A The fact is that Mariah has only displayed a range of BbG which is very close to a full  octaves Bb has only been displayed in an interview and G has been hit twice in live performances of Emotions and seemed fairly easily done Besides Bb she has hit C numerous times Emotions My All You And Ilive performance and other songs have C as their lovest Besides G F is her highest in the studio version of All In Your Mind