All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
If the hair is down to the shoulders, then wiping the part that extends below the head boundaries doesn`t avail a person. If a woman`s hair was folded on top of her head, then it doesn`t suffice to wipe it. Rather, she should wipe the hair within the head`s boundaries. Therefore, we recommend that she wets her hand and inserts it into the roots of the hair. By doing this, she makes sure that the water has reached the head, or, at least, the hair within its boundaries. Moreover, it is preferable that the person doing Wudoo` wipes the entire head from top to bottom then back to the top, following the guidance of the Prophet Mohammad {PBUH} in this regard. As this is easier for men than women, the latter should suffice with the aforementioned. And Allah Knows Best.