Is it permissible to pay Zakat to prepare a female relative for marriage or to help a poor and destitute family?

If the girl is unable to prepare herself with what is customary, and she will not marry except with this provision, and it is permissible to give her zakat without extravagance, and you intended, when paying the money, that it is zakat, then you have fulfilled the obligation and are not required to give out zakat again. However, if she is able, or you paid the money without the intention of it being zakat, then it is not permissible to count it as zakat.