She doesn't register "Xemnas" as anything, since it's out of her familiarity. However, she does indeed notice the immediate discomfort her announcement has made the girl. No, more than that, she's downright afraid. Did she not really look at Sakura's face before? It's true that when acting as Number 1, she wears makeup to look like a living human. Her real face is rather frightening, and perhaps she ought to remember that, though it stings a little to be treated with such fear.

"Sorry... I know I look terrifying," she apologizes, giving the girl proper space so as to not appear threatening. "I'm a zombie, so that can't be helped, but... I promise I'm not anyone scary."