What is the ruling on a wife accusing her husband of a relationship with another woman without proof, even if she asserts this to her parents?

A wife is not permitted to accuse her husband of committing haram without clear evidence, for Allah Almighty says: "O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin." This verse prohibits His believing servants from many assumptions, which include accusing and suspecting family, relatives, and people without valid reason, because some of these assumptions constitute pure sin.