Congrats on quadrupling the size of your chapter!
We got a little bit of what I think you're talking about when we held informal recruitment. The people who come out for IR really want to be there with your GLO - whether they come out with their minds made up that they want to join, or just to find out more about what your org is about. This is unlike NPC's formal recruitment, where sometimes you can just tell that someone is only there because she has to visit all her options and she can't wait to leave.
I'm a little curious - you say you're getting these 20 women but they haven't pledged yet? Do you do your membership selection in the fall but not actually start the pledge program until spring semester? I'm wondering because when we get new members, we can't wait to slap a ribbon on them - even if, for some reason, we hold off on starting their actual new member education.