whoops do you know what it is the director wants to do but can't because the other director is away? And would you be happy with that?
If the solution is there but needs to wait for someone to get back from holiday might be worth waiting? Unless v long holiday of course!
I hesitate to advise someone to leave their job, but it does sound like you feel even if a solution is found, it may happen again in 6 months; is it the case that this will keep happening while these other women are there?
Alternatively is there anything you feel the directors could do which would actually stop it for good? If so, you need to specifically say they need to do X (disciplinary procedure against these other women, or whatever other action you think will achieve what you need) or they may lose you.
Other option would be bringing a formal grievance - don't know enough to tell but this could well be bullying, and the directors have failed to satisfactorily address the situation following your informal discussions with them.
I think you really need to think about what the best end outcome would be for you - would there be any resolution that would stop it entirely - it may be that even if the individuals in question are disciplined, it may well not help the atmosphere at all, or could make it worse, certainly while the procedure is ongoing. Only you will know whether some kind of formal action will work, and as I say, if there is something you can think of which the directors could and should do, request this specifically.
Depending on how bad it is, in terms of legal action really probably your only option would be a claim for constructive dismissal on the grounds that your position has been made untenable by this situation and the failure to address it. Constructive dismissal is v v difficult to prove and stressful to bring, so I would say consider all the other options. You could however indicate to the directors that you feel your position is becoming untenable, to push them into some kind of action.