The highest I've ever heard her sing was an "F" (F5, an octave above middle "F") and the lowest I've ever heard her sing was a low "F" (F3, an octave below middle "F").
But the highest she's been hitting recently is an E flat ("GREEN," "Rule"), two half steps below the "F" she used to hit.
So, seems like she has a little under three octaves...
But that's just the information I can gather as a singer myself. This isn't from any other kind of source.
