My FI's aunt is a widow who has started dating again and is being invited with her long-time boyfriend. I know the proper form for widows is usually as Mrs. (either with the deceased husband's firstname/lastname, or her first name, his last name, depending on her preference). But since she's dating again and we're inviting her boyfriend along with her, it feels really weird to address the envelope to Mrs. FI's Aunt and Mr. New Boyfriend. Does she go back to "Ms." under these circumstances?