my friend was married to a man say BEN and later found out his real name was JOHN. She wants a divorce now. Was she ever legally married at all?

Short answer, yes (probably).  I was hired as an expert a few years ago to review exactly such a situation, and in Nevada simple error (or falsification) of data on the marriage license application may be a misdemeanor, but does not invalidate the resulting marriage.  of course, there could be other defects -- if "John" falsified his name beause he was already married to someone else, under any name, that would be a different matter.  It is uncertain what the facts are, and even whether the marriage was in Nevada (if not, the laws of the place of marriage would be the applicable ones to research).  If the marriage was here, an annulment could be sought here even if no party is a resident, as explained here.  Annulments in this state require a legal process, but do not "take forever."