Given that the GOP leads among married women already, and given that the number of older married continues to gain on the number of younger unmarried women, and given also that the vast majority of unmarried women seek to become married women, we can assume that at some point in time, the GOP will outpoll the Dems in women in general.
Ever heard of divorce?
Generally, women in a healthy relationship with a man are more likely to vote Republican. Women who are angry at men, for whatever reason, are more likely to vote Democrat. It's purely anecdotal, but I think it's pretty accurate.
Women favor Democrats because girls are not raised with the drive toward independence that boys are, generally. Women therefore don't see as much wrong in dependency on government at some level as many men do, in general. That leans women more in a Democratic direction than men.