Is a wife who disobeyed her husband's command regarding visiting a friend and returned home considered to have committed Zina (adultery), and does that entail her becoming forbidden to him?

The disagreement among scholars regarding the ruling on a man saying to his wife, "You are unlawful to me" or "You are forbidden to me," has been previously explained. The preponderant opinion is that it depends on the husband's intention: if he intended divorce, it is a divorce; if he intended ẓihār, it is ẓihār; if he intended īlāʾ, it is īlāʾ; and if he intended an oath, it is an oath. He is then bound by the consequences of that intention. Accordingly, your statement to your wife, "If you go, you will be forbidden to me," and she did go, results in what you intended: ẓihār, divorce, īlāʾ, or an oath, and you are bound by its consequences. If you did not intend anything, then an expiation for breaking an oath is required of you.