Why does mother-in-law always lie? She always said that her daughter bought everything, even a broken mobile phone lied that it was her daughter's mother's day.

The old lady wants to show her daughter's filial piety and make her face shine. One may worry that others will look down on her (children are unfilial, parents really fail! Secondly, it may be to let your daughter-in-law learn to honor her elders. But then again, my mother was never like this. She has enough pension and feels independent of her children, self-reliant and decent.