Is it permissible for a woman who has only one brother and other heirs from deceased brothers' children to bequeath all her land to her niece, or to donate it for the construction of a mosque, and what is the legitimate distribution of the land in this case?

If a woman wishes to gift all her wealth to her sister's daughter during her lifetime, this is a permissible gift, unless her intention is to deprive her heirs, in which case it would be a prohibited stratagem. She is also permitted to donate her money for building a mosque or for other purposes, provided she is able to provide for herself and those she supports. However, if she intends to bequeath all her wealth after her death to her sister's daughter or to the mosque, her will is only enforceable up to one-third of her estate. Anything beyond that is subject to the approval of the heirs.

In the event of a woman's death, if she has no father, no child, and no husband, and she has only one brother, then this brother inherits everything she left behind.