Is the financial transaction conducted by the mother's friend, which involves buying a commodity directly from a merchant and then selling it to a buyer in installments with an agreed-upon profit increase, considered unlawful?

If a woman conducts her contracts with her customers in the manner described, then what she does is forbidden by Islamic law because she has lent the buyer cash with usurious interest. For the transaction to be valid, she must purchase the commodity for the one who ordered the purchase, and it must enter into her possession and liability, then she sells it through a separate contract. What she is doing is merely a trick to engage in usury, and it is not permissible for her to do it, nor is it permissible for her mother to give her money for this purpose. If she earns a profit from this, she must dispose of it and spend it on the welfare of Muslims and give it to the poor and needy. She must also advise her friend to correct her transactions by first buying the goods and then selling them to the customer.