Is it permissible for a wife to buy gifts for her family without her husband's knowledge, using money that the embassy sends to her monthly, which she considers her own personal salary?

If the money sent from the embassy is explicitly divided between the spouses, then it is the wife's property, and she is permitted to dispose of it without her husband's knowledge, although informing him would better preserve affection. However, if the embassy did not specify a division, and the division was only understood from an increase in salary for the married person, then all the money belongs to the husband, and the wife is not permitted to dispose of it except with his permission.