Right, correct me if this is no longer the case, but I believe that:
-Best man organises stag night
-MOH (or bridesmaids) organises hen night
-Bride does not have much (if any) say in the 'w's' of hen night -who/when/what/where (same for groom)
This certainly was the case when I got married - I did not have any say in my hen night arrangements other than to suggest who I would like to attend it (which my sister promptly ignored).
Recent events in my life, plus some posts on here have led me to believe that maybe things have changed dramatically and I am old-fashioned and weird in thinking this way...