Does a woman's spending from her private money on orphans under her care count as Zakat for this money for many years past, and what are the Shariah implications if this spending does not suffice for Zakat?

The madhhab (school of thought) of the majority of scholars is that zakat is obligatory on the wealth of a child and an insane person if it reaches the nisab (minimum threshold) and a hawl (one lunar year) passes over it. The questioner must repent and pay zakat for the past years, even if that leads to the loss of more than half of the amount. Orphan's money should be invested away from interest-based banks. The lack of spending by grandparents and paternal uncles does not justify not paying zakat.