The ruling on a woman sleeping with another woman in the presence of a non-mahram man

This is a message we received from the questioner (A. B. A.) from Yanbu al-Bahr. He says in his message: I am a married man, and one day my wife and I traveled to the home of my brother’s wife’s family. We were sitting there, and my wife laughed a lot, and I did not approve of this. During this, I hit her on her leg, so she got angry with me and went to sleep with my brother’s wife’s sister, and this sister had an unmarried brother with her, and they all slept together until morning. What is the ruling on this in the Shari'ah? I have a doubt about my wife, so please inform us, may Allah reward you.
Answer: In any case, regarding the excessive laughing, you did well in forbidding her from this, and hitting her, provided the hit was light and minor and did not harm her. Her sleeping with the woman while a non-mahram man is present is a mistake, and you should not suspect her; because a woman may be careless and lax if she is covered, veiled, and concealed. However, her sleeping in a place where there is a man who is not a mahram to her is a mistake on her part; because something of her may be exposed, or something of her may be seen. So she should not sleep in a place where there is a non-mahram man. But this does not obligate you to have a bad opinion of her or to divorce her. Rather, you should advise her and guide her so that she does not return to something like this, and there is no harm, if Allah wills. Yes.
The presenter: May Allah reward you.