Which Buddhist traditions have no gender divisions at all

I had a conversation with a friend and she was very upset that there were some gender division in the group I practice with. We have some single sex retreats and some study groups are single sexed. But mostly things are mixed. If my friend wanted to practice Buddhism with a group with no gender divisions whatsoever - what group would that be? So all study, retreats, events would be mixed and if there is a monastic community then that would be mixed too.