Are we talking about the absolute number of female pilots (one would expect a large legacy carrier to lead) or the percentage of females (here a small new start up would probably lead)?
As has been mentioned there is no reason why an equal number of females will want to become pilots. When I used to hang out on roof gardens there were far more men than women - although not 100%. I believe fundamentally that people should not be barred from doing the job that they want as a result of their gender or any other factor (other than ability). This is not the same as saying that there should be a quota even a 50% quota as has been suggested for some industries. (Think of the impracticability of it over the workforce as a whole.) You could argue that the key issue is the proportion of applicants from females. I suspect that they key issue these days is in any case not your sex but what passport you hold. (Try getting a job with an American carrier if you are not a US citizen. Its true elsewhere and Brexit may not help.)
There will be a cohort effect as women take a long time to work through the system. Given the incremental seniority based systems used by legacy carriers it will take many years for anything to change. Seniority based systems are effectively based on how old you are when you join and pay may not be always be matched to experience Would this be picked up by some as a reason to move away from seniority. Lots of legacy airlines will say that we really don't want to go there.
Tied in with the last two points, should rosters be made to help out women? Again seniority doesn't help but its a far bigger issue than this. If women are given special advantages this would affect men who may well have a working wife and have domestic responsibilities (and some feminist groups see everything as a one street for women forgetting that men have issues as well). A Virgin style rotating seniority for rostering could help - but will it happen?
Let me stop before I get more controversial and upset more people...