What should I do regarding my mother who committed adultery, knowing that I witnessed it when I was young, and she was the one who raised me after my father's death, and the matter still haunts me even after I grew up?

It is not permissible to accuse anyone of adultery based solely on suspicion or rumor, because the Lawgiver has stipulated stringent conditions for its proof, which are: confession, or the testimony of four upright witnesses who explicitly observed the act of adultery. If adultery is proven, then the perpetrator must offer sincere repentance. As for the parents, their rights to dutifulness do not fall, even if they commit acts that violate the Sharia.