I wonder if it a money thing. The cost of most things in Aviation is high and I wonder if women (in general) cant justify the cost to themselves, whereas men (and again this is very general) will try and justify it, forsaking all else.
My wife has a PPL, and in the small number of clubs or airfields I have visited or been a member of, I just havent seen any discrimination against women, nor the need to have to prove themselves any more than men. I would probably say that most people realise there arent many women in aviation, and all are welcomed and want to keep them in the community.