What is the ruling on a woman wiping over her khimar when performing ghusl after major ritual impurity (janabah), and is this permissible if it is difficult for her to wash her head every time?

Wiping over the khuff (leather socks), turban, and khimar (head covering) is not permissible in a state of janabah (major ritual impurity) by consensus, and is only permissible for wudu (minor ritual ablution). There is no problem in washing the head from janabah; it suffices to pour three handfuls of water over it without undoing the hair, as Umm Salamah did. As for necessary coverings like a splint, it is permissible to wipe over them for both major and minor ritual purifications as long as the need exists, based on the Prophet's (peace be upon him) saying regarding a head wound. Paradise is surrounded by hardships, and it requires patience and striving in obedience to Allah.