IMO, women are generally more likely to take a NRA Basic class or other type of basic class than men. Most men think they know firearms, how to shoot and basic classes are not for them. Thankfully, the NRA requires the basic classes as a prerequisite to more advanced classes.
As far as the more advanced classes, it seems there could be several factors why most women do not take advanced courses.
Here are possible factors I see.
First, the idea of possibly needing to shoot a person or animal to stop a threat is something most rational people don't want spend a lot of time considering. IMO, most women find the topic harder than most men and are more likely to avoid the subject/courses.
Second, if a lady has already been a victim, they are not going to want to possibly relive the attack during the course in front of strangers - especially men they do or do not know. Women are different than men in several ways, and one area is the difference in emotions and displaying their emotions. They may be fearful of how their emotions may come out during a more advanced course that deals with personal protection.
Third, if a lady had a bad experience with males and their attitudes/treatment of women in the past, there is a tendency to want to avoid a possible repeat of that situation.
Fourth, did they take a course or have a range session where the male instructors and range officers flocked to them while on the range? If they have the attention of multiple instructors/range officers and are given multiple versions of how to do this and how to do that, it is not going to be pleasant experience. It is also not going to be a pleasant experience if a female who looks somewhat like Barbie has help from multiple instructors/range officers at the same time while a female who does not look like Barbie has very little to no instruction on the range. This is an area where the lead instructor and chief range officer really need to take charge. Define what is expected of the instructors/range officers before the course starts, and remind them again as a group before the first range session. If you see multiple instructors/range offers with a female student, immediately see why this has happened and address the situation if there is one. If there is a male instructor/range officer who always seems to make his way to the female students, talk to that instructor/range officer regarding this conduct. For the male instructors/range officers that have a tendency to migrate to female students, assign them to a male student.
In summary, I think it comes down to making the female students comfortable about the course. If they are not comfortable, they are less likely to take the course. Women are more likely than men to avoid possible conflicts.