Is the son obligated to fast the month of Ramadan that his mother intentionally missed, and is charity sufficient for that?

If the mother is alive, she must make up the days she missed in Ramadan due to pregnancy and postpartum bleeding, repent for delaying the make-up without a valid excuse, and pay the expiation for the delay by feeding one poor person for each day. However, if she has passed away, and she was not negligent in making up the fasts, then no fasting is required on her behalf. But if she was negligent, scholars differ regarding the permissibility of fasting on her behalf.