The Talmud examines this scenario:
A man vowed that his son-in-law can have no benefit from him. Now he wishes to give his daughter money. He cannot do this directly, as anything acquired by a married woman belongs to her husband, but he can say to her: This money is hereby given to you as a gift, on condition that your husband has no rights to it, only that which you pick up and place in your mouth.
As we learned in Ketuvot, the default situation in a Jewish marriage is that whatever resources come to a married couple legally belong to the husband, who has a corollary responsibility to use everything for the good of the family. Jewish law requires that the husband feed and clothe his wife appropriately and put a roof over her head. This law applies even when the whole financial burden is upon him, and all she adds to the household balance sheet is a few balls of yarn.
So in theory this woman is already being taken care of, but her father wants to give her more. Now, he could have given her a kind of dowry that is her personal items to use. There is also a certain type of dowry that a husband can make use of or invest but must return the full value of if the marriage ends.
What this case describes is something more extreme. Here, the wife’s father wants nothing to do with her husband and has vowed that he get no benefit from him. So he doesn’t even want to give extra dowry since the husband will have title to it.
However, he still cannot give his daughter an independent source of wealth, only money for food. Since she is already getting food from her husband, she can sell what she gets from her husband and have some extra spending money.
The general idea here is that our sages wanted a method for a father in law to benefit his daughter without also benefiting a son in law that he hates. However, they did this in a way that does not allow the father in law to undermine the husband’s role as the primary provider.
Married people need to have proper respect for in laws but also an understanding that their goals and interests may not align with our own. Parents and in laws may be generous but their gifts may come with certain expectations or conditions.
It may be healthier for everyone involved for the married couple to work on becoming financially independent so they are able to say no to a gift from the older generation that causes a burden on their own relationship.