What is the ruling of Islamic law concerning dealing with a negligent and harsh mother who seeks financial exploitation, while avoiding visiting her for fear of dealing with usurious money, and sufficing with checking on her by phone?

The mother is the most deserving of kindness, benevolence, and maintaining ties of kinship. Her right does not fall due to any shortcomings she may have committed towards her son. Although her refusal to breastfeed her son is a matter of scholarly disagreement, at most, she would be sinful for abandoning a duty, but this does not justify mistreating her. As for her request for money, it is obligatory to spend on her if she is in need, and not obligatory if she is not. However, it is recommended to do so to appease her, unless it is known with certainty that she will use the money for usury (riba), in which case it is forbidden to give it to her. Her request for a visit must be answered kindly, and it is not permissible to suffice with a phone call. The fact that she deals in usury does not justify abandoning visiting her. Rather, one must avoid accepting any of her money that is certainly or most likely from the essence of usury.