Widows shave their heads
To ward off evil spirits and sometimes death, women are expected to shave their hair when their husband dies. Some say the dead spirit of the husband lingers in the wife’s hair and so it serves her well to shave it for her own good, otherwise misfortune may follow her.
Other cultures do not force the widows to shave their hair but they are not at liberty to add extensions or dye them. The underlining thing here is showing that you are grieving your husband well by keeping your hair out of the way is a sign of respect to his family.