Is a woman's spending on orphans from her private money considered the equivalent of paying the obligatory Zakat, and if not, must she pay Zakat retroactively for previous years?

A woman paying her Zakat to her orphaned children is not permissible, because the benefit would accrue back to her by protecting her wealth. Therefore, she must pay the Zakat obligated upon her for the past years to those who are deserving of it. Depositing money in banks is permissible if they are free from usurious transactions; otherwise, it is not permissible except in cases of extreme necessity.