She has an insanely good mix.
Very strong.
That is not chest, so it's not too vocally taxing (most of the time, at least).
The sound is very much in her head, and that's what makes her belt so light and easy, but still powerful.
I think her voice will stay like that so long as she doesn't get lazy and use her throat.
Eep!
And falsetto exercises help in obtaining those higher notes (for guys).
And practicing those warmups - they're not just for warming up.
Personally, I think I have too much bloom.