Is the debtor obligated to repay the charity money she took for her husband after the death of the owner of the money, knowing that the owner of the money was aware of the debtor's difficult financial circumstances and had forgiven her debts before her death?

A poor person is not permitted to ask for charity on behalf of another and then take it for themselves, because the giver of charity intends for it to reach someone else, not for the one who asks to take it. Whoever does this must repent to Allah and not repeat such an act. If the owner of the money dies and cannot be informed, the poor person who received the charity is not obligated to guarantee the money if they were a deserving poor person, because the charity reached a poor person. Your female friend's acquittal of you applies only to the debts you are aware of.