Is it permissible to give zakat to an unmarried sister, knowing that she has a monthly salary and an inherited amount in the bank?

The poor person eligible for Zakat is one who does not find what suffices him and those whose sustenance is incumbent upon him, including food, clothing, housing, and medicine. Therefore, whoever has what covers her essential needs does not fit the description of poor, and it is not permissible for her to take from Zakat. However, if they both do not find what suffices them to cover their essential needs, then it is permissible for each of them to give her Zakat to her sister.