I have no doubt that she can sing, but I've yet to see her give a performance where she's singing in time to the music and has a real connection to what she's singing. I first noticed the lack of rhythm/timing on BGT. I thought it was something she'd get to grips with in time, then I saw a performance from her on TV this year (guest performance on BGT, I think...when she was singing a Madonna song) and she was still ignoring the tempo of the music and singing at her own speed.
Well then you didn't see her in NYC in 2009, or in Japan in 2009, or NYC in 2010, or in Newcastle in 2012 . She doesn't sing the song like Madonna sings it, she intentionally sings it at a slower pace. On AGT she transformed You Have to Be There
from a song of desolation to into a song of power. Sorry, I've never seen a performance which would give your comment any credence.