Women should not dress as if to draw attention to themselves. That is the entire point of niqab. When a woman wears her hair in a bun-like, hump-like manner, it shows through the hijab. What is now the point of the hijab? Some sisters have the incorrect idea that hijab means to cover the hair and it does not matter if they wear tight clothing or that their scarf itself is decorated with glitters or other things that attract attention. If sisters want to wear such things, then wear another piece of clothing over them when in public and amongst ghayr mahram. But, if a hairstyle shows through the hijab, then it defeats the purpose of the hijab.