My question is that I’ve seen a lot of responsa about whether or not to inform a husband about the adultery of his wife. Are there any sources discussing informing the wife of the infidelity of her husband?

The responsa you refer to are halachic (!) issues which may prohibit the husband to continue living with his wife, forbidding (!) the husband to choose to “forgive and forget”, even if she sincerely apologizes, and he would like to accept her apology. Contrarily, regarding a husband who is infidel, albeit prohibited, disgusting and unacceptable behavior, if he sincerely regrets and apologizes, the wife has the prerogative to forgive and prefer to continue their marriage, should she choose to do so. This is just regarding halachic prohibitions regarding the very continuation of the marriage or not. Regarding the sanctity of marriage, obviously the relationship is supposed to be and must be mutually exclusively intimate, holy, open and honest from both sides.