Is it permissible for the wife to send a monthly sum to her well-off family without her husband's consent, especially if that could lead to divorce?

A wife's salary is her exclusive right, and the husband does not have the right to prevent her from donating it to her family. This is not extravagance but rather a righteous deed. If the husband has sworn by divorce that she should not donate her money to her family, the ruling depends on his intention when taking the oath, keeping in mind that swearing by divorce is an oath of the wicked and can have severe consequences.