Is the ninety-year-old aunt, who is in a semi-coma and sometimes curses God and blasphemes, sinful? And is this considered a bad ending? What should we do for her? And how can a Muslim avoid such a situation?

As long as the woman does not comprehend what she is saying due to the dominance of her intellect (i.e., loss of mental faculties), she is not held accountable for what she utters, for intellect is the basis of accountability. What afflicts her is not considered a bad ending, and good is hoped for her from Allah if she was righteous before her illness. To avoid such a state, a Muslim should pray to Allah not to return them to the most decrepit age and to grant them enjoyment of their hearing, sight, and strength.