Is it permissible for a mother to give gold to her daughter to help her with marriage, without giving similar gold to her married son who is financially well-off?

Parents must be just in giving gifts and grants to their children, with the male receiving twice the share of the female. As for maintenance, which is what is given to a son or daughter to meet their needs (such as education, medical treatment, or marriage), what is obligatory here is justice, not equality. This means that each child should be given what suffices them according to the father's need and the parents' financial situation. So, whoever is in need receives, and whoever is not in need does not. For example, if one of them needs to get married and the father does not have surplus money, he is not obligated to give it, whereas if the father's financial situation is easy when another child needs to get married, he is obligated to give them what suffices them.