What is the way to deal with a mother who disowned her daughter, threatens her with murder, whose psychological state changes, who betrays her husband, and incites him against their daughter, while it is impossible to inform the sick father?

It is obligatory upon you to honor your mother and be good to her, no matter what her actions are. Among the greatest forms of kindness is to strive for her betterment by supplicating for her guidance and righteousness. If it becomes clear that she is psychologically ill, then you should seek to have her treated with the help of your wise relatives. If you fear for yourself from her, then seek protection with your brothers, paternal uncles, or maternal uncles. Beware of accusing her of indecency, for Allah the Almighty says: "Indeed, those who accuse chaste women, unaware [of the evil], believing — are cursed in this world and the Hereafter; and for them is a great punishment." And her love for another man does not necessarily mean that indecency has occurred. If her relationship with another man is proven, then whoever becomes aware of it must advise her, remind her to repent, threaten to expose her affair, and strive to prevent this evil.