How can my mother purify herself and pray after a hysterectomy, given that there are covered wounds preventing water from reaching them, and the bleeding has currently stopped? Is the nursing staff's purification after the operation sufficient for her to pray?

A small amount of blood is excused. However, what is mentioned in the question is considered a large amount of blood that is not excused and can only be purified with water. If the mother is unable to purify it, she should perform ablution and pray. If she recovers, she should purify herself and repeat the prayers she performed while impure.