What is the ruling on divulging a wife's private secrets, including her problems with her in-laws, to a friend who later turns out to be untrustworthy and a liar? And is it obligatory to sever ties with this friend who exposes the faults of others?

Lying and backbiting are forbidden in Islamic law. Lying leads to wickedness, and the backbiter is like one who eats the flesh of his dead brother. Backbiting is your mentioning your brother with what he dislikes. What the woman does by mentioning people's faults is forbidden backbiting, unless it is for a legitimate Islamic benefit, such as seeking redress or advice. One must rebuke the backbiter, and if they do not respond, one should leave the gathering. This woman should be advised and warned about the consequences of her actions, and if she persists, then there is no good in her companionship.