What should a son do if his mother hates his wife and curses her family, and describes him as disobedient for not giving her money?

If the mother curses the wife and her family without justification, then she is an oppressor. She should be advised gently and politely, without violence or abuse. As for her request for money, if she is in need of it and you are able to give it to her in excess of your own needs, then you must do so. If she is not in need, then it is not obligatory, but it is preferable to give her what you can without causing yourself hardship.