For me I use my wife as the assistant instructor to get women through the door. The ones i usually get are either interested more in me than what I'm teaching (here is my WIFE the assistant instructor, which usually scares them off) have had something happen to them that made them realize they need training (and could care less that I'm a man), or ones that have came in with some one else (sister, friend, parent, whatever). Usually when i talk to them to convince them to join they are 'shy' or nervous, until i introduce my wife as the assistant who will be primarily working with them that day. After that they seam much more interested in participating. From there i try and use them after a while in the demonstrations to get them used to dealing with bigger guys.
There has been a good mix of men and women (non husband/wife teams) in the CHL classes though, so that's a start.
"Once they solve the problem, get over the fear, or just get distracted they stop attending."
I have noticed that as well, i get quite a few that ask self defense questions during CHL classes that are not interested in overall training, they just want that question, that scenario answered. I also had one lady argue that the 2 hour lady's self defense course she took was the be all end all (All you need is a kick to the groin, end of discussion).
Just reenforces the importance of drills that involve protecting a 3rd person (wife/GF/whatever)