Demi Engemann may only be a "friend of" the cast in season 4 of "The Secret Lives of Mormon Wives" ... but TMZ has learned she filmed far more than a typical part-time player. Sources close to production tell us the exiled cast member's role goes well beyond the usual drop-in appearances. We're told Demi was mic'd up for multiple events and logged significant camera time before her involvement eventually tapered off. Demi starred in the first two seasons before being iced out of the "MomTok"