Is it permissible for a wife to uncover her face before non-mahram men to avoid displeasing her mother, while the wife insists on covering her face to please Allah?

A Muslim woman must cover her face from non-mahram (definition) men. The obligation of hijab (definition) in front of the husband's relatives (non-mahrams) is even stricter because their interaction is frequent. That is why the Prophet, peace and blessings be upon him, said: "The in-law is death." The husband must support his wife in her commitment to the lawful hijab, and gently explain to his mother that this is a religious ruling that cannot be compromised, and there is no obedience to a creature in disobedience to the Creator.