Hm, I think her beltings in the higher register are forced or maybe better to say shrill, but this may be my subjective impression.
Nevertheless she is a great singer.
I could agree that they are sometimes kind of shrill, but I think she uses it to great advantage. For example, in Freakum Dress at the end when she is singing "Yeaaaaaaahhh" it just has this sense of incredibly urgency and a sense that she is being overpowered by some emotion just that has to be let out. The same goes for End of TIme when she sings, "Bring your love to Meeeeeeeeeee".
