Is it permissible for a woman experiencing irregular bleeding (istihadah) to pray the night vigil (qiyam al-layl) with the ablution (wudu') of the 'Isha prayer after half the night has passed?

This issue is a matter of dispute. Some scholars are of the opinion that if half the night has passed, she must renew her ablution. However, the more sound opinion is that she is not required to renew her ablution.