What is the ruling on recovering money from a deceitful beggar by deceiving her into believing she will be given a larger amount in exchange for the money already given to her?

If a charity falls into the hands of someone undeserving, Allah Almighty records its reward for the giver. It is not permissible to revoke a voluntary charity, even if it becomes clear that the recipient was not deserving of it. However, if the charity was obligatory, such as Zakat (definition), and one's obligation is not fulfilled by giving it to an undeserving person, then it is permissible to reclaim it.