Question:   A woman who has due Mahr from her husband which is equivalent of nisab of zakah but has no other cash or savings, can this woman receive zakah money?

Answer: If the husband is capable of paying the mahr cash on instant demand by his wife, then she will be regarded as a wealthy woman and she will not be allowed to receive zakah. However, if the husband is not capable of paying it instantly and the mahr itself is not payable instantly (due to a contract for paying it later) then she can receive the zakah money as mentioned in the question.

Reference: [1] Fatwa Shami vol-6:312