How are the funds in the bank-deposited account distributed between the orphaned boy and girl, and does the mother have a share in them, knowing that the boy is over 21 years old and working, while the girl is still a minor?

If the donors stipulated conditions for the disbursement of the money, then these conditions must be adhered to. If they did not stipulate any conditions, then the money belongs to the two orphans, and the mature, sane orphan should be given his share, while the share of the one who has not reached maturity should be safeguarded. The money should be divided equally between them because it is a gift, not an inheritance. It is obligatory to avoid depositing the money in interest-based banks; instead, it should be placed in an Islamic bank, or the guardian should invest it through trade, as the Prophet, peace and blessings be upon him, said: "Whoever is a guardian of an orphan who has wealth, let him invest it and not leave it until sadaqah (charity/zakat) consumes it."