Is it permissible to pay Zakat from one's personal money on behalf of one's mother who refuses to do so due to psychological and mental disorders?

If the mother is sane and owns wealth subject to zakat, she is responsible for paying her zakat. It is not permissible for the son to pay zakat on her behalf, whether from his own money or hers, due to the absence of the intention (niyyah) condition. However, if she lacks legal capacity, zakat is obligatory on her wealth, and her guardian is responsible for it. In this case, the son, in his capacity as a guardian, may pay the zakat from her wealth or on her behalf from his own private money.