Is the previous ablution (wudu') invalid and must the prayer be repeated if the questioner wiped over her head covering (hijab) without being in a state of ritual purity (tahara) when she put it on?

The ablution (wudu') of a woman with chronic discharge (mustahadah) is valid according to many scholars, due to her wiping over part of her head. This is the madhhab of the Shafi'is and a view among the Hanbalis, and there is no harm in following it. As for wiping over the khimar (head covering), the Hanbalis permit it if it is wrapped under the chin (or throat) and the woman wore it while in a state of ritual purity (tahara).