danielryan saidthe girl has used her voice quite a bit. when rested and with no alcohol she still can sing.
I'm currently at work and youtube is blocked, but you need to go watch 2 things.
1 - Her 2006 Grammy Performance of We Belong Together and Fly Like A Bird -- 100% live and amazing.
2 - During a tribute to Patti Labelle she sang If Only You Knew/Over The Rainbow - Her vocals are insane!
I totally agree with you, especially about the Grammy performance of We belong together& Fly like a bird.
However, even then one could notice that she's under a lot of pressure on stage and her voice doesn't come out as easily, as it used to.
My theory is that she hasn't been singing correctly over the years and that's the reason for losing her vocal abilities... it's sad, she really was something.