Is zakat obligatory on a sum of money received as deferred payment by a divorced woman who is unemployed and has no source of income other than the child support for her children, when a full year has passed over this sum?

A woman must pay zakat on her bridal gift for past years after receiving it. Zakat is due on it each time a hawl (lunar year) passes. She must hasten to pay the zakat, for charity does not decrease wealth, but rather increases it.