Is it obligatory to obey a mother who prevents her daughter from giving charity or asks for money designated for charity when she does not need it?

If the charity (sadaqa) is obligatory, like zakat, then it is not permissible to obey the mother in preventing its disbursement. Rather, it must be disbursed because it is one of the pillars of Islam. However, if the charity is not obligatory, then it is obligatory to obey the mother in preventing it, because if an obligatory matter conflicts with a recommended one, the obligatory takes precedence, by agreement of the scholars. But if you disburse it secretly without her knowledge, this is good.