What is the ruling on the wife forgiving the half of the *mahr* that she has already received or taken possession of before the divorce?

Primary text

If the wife wishes to forgive the portion of the *mahr* that has already settled in her own liability (either because she received it and used it, or it was lost in her possession), the pronouncement of forgiveness is invalid. This is because the half she is entitled to was already her property, and her disposition over it does not establish a liability against her. The husband's ownership over his half only solidifies upon the divorce, and thus nothing regarding her half is established as a debt upon her.