You are required to advise your mother and warn her against
verbal abuse, especially if it is addressed to the dead, because they have attained the result of that which they had done in their life. Accordingly, we should only mention the virtues of the dead and refrain from mentioning their bad deeds. Your mother must remember the positive aspects in her life with her dead husband, for Allah says,
And do not forget liberality between yourselves.
The Prophet (peace be upon him) said,
Do not abuse the dead, because they have attained that which they had forwarded (i.e., their deeds, good or bad).
Al-Bukhari in his Sahih (authentic) Book of Hadith)
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.