What is the ruling regarding the university expenses that a mother sends to her son, if he believes that her money comes from sorcery and witchcraft?

Accusing people of sorcery and witchcraft is not permissible except with evidence. If you are certain that your mother earns her money through sorcery and witchcraft, then this money is unlawful (haram), and it is not permissible to accept it or benefit from it, unless you are poor and unable to support yourself, in which case it is permissible for you to take only what you need from it.