Following the Prophet’s guidance, the impurity of a dog is to be removed by washing the vessel seven times, one of which should be with soil.

One cannot pray in impure clothes because of the general meaning of the texts which indicate that clothes should be pure when praying. They do not differentiate between dry impurity and wet impurity. Impurity cannot be removed from a garment except by washing it with purifying water. It is not sufficient merely to let the impurity dry out.

If these discharges come as the result of intimacy, then they are pure, because they are not the waste products of eating and drinking, thus they are not urine. Based on this, she does not have to wash her underwear or change them if these discharges get on them.