Is it permissible to give zakat to a divorced sister with a low income, or is her financial support obligatory and not counted as zakat?

If the divorced sister is unable to earn a suitable living, her maintenance is obligatory upon her capable father. If her income is insufficient to meet her needs, the father is obliged to supplement her maintenance if he is able. If the father is unable to pay all of the maintenance, the obligation transfers to the brother according to some scholars (such as the Hanafis and Hanbalis). In this case, it is not permissible to give Zakat to the sister.