Once is enough, for women from the forehead till the nape of the head but the sunnah is to do it once more to the front! You can fix your hair afterwards.

In wudu, is it enough to just wet my hands and pass it from my front head to back head once without coming back to front head again? What about the sides of the head sir? And should the water reach the roots of hair or is it enough to just pass from over the hair, I mean just surface of head.