Is it permissible for a woman to wipe over her Khimaar (head covering) when performing ablution?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The scholars differed in opinion with regard to the issue of wiping over the Khimaar (head covering) without a necessity. The majority of them are of the view that it is not permissible to wipe over the head covering unless the water reaches the hair. However, according to the established opinion of the Hanbali school, this is permissible, which is, the most preponderant opinion that is supported by evidence. Bilaal narrated that the Prophet said: "Wipe over your socks and Khimaar [for women].” [Ahmad]  The above narration is also reported by At-Tirmithi, An-Nasaa'ee, and Ibn Maajah with different but close wordings. It is also confirmed that Umm-Salamah used to wipe over her Khimaar. Nevertheless, the Hanbali School conditioned the permissibility of wiping over the Khimaar on it being turned over the neck and over the chest, as this is the one which is difficult to take off when performing ablution contrarily to the one which is spread over the head and down on the shoulders and body.     

Allaah Knows best.