I don't think that the subject here is the number of women doing gambling. The research is just showing us the gender approach in gambling whether as stated, men do like skill-based games while on the other hand, women are mostly on luck-based games.
I don't think that works that way. Women and men do have their own perception in gambling. I've seen many women playing poker and other pvp skill based gambling games. The only reason why we think women preferred luck based games like slot games is because there are only few of them who actually likes gambling and some of them don't want to dwell along with men in the same table, because the society thinks a woman who gamble along with men is as good as a slut who will never hesitate in selling her own body when she runs out of money to gamble. That's the stereotypical mindset of the society who sees a woman who gambles.
Also, they are too shy to play with other men in gambling, but right now, because of the online casino, you can't know if your opponent is a woman, unlike before, when you'd become a head turner if you were a woman going to a casino on your own and you'd see a lot of men try to catch you. But again, right now, women can freely play it through their homes without being noticed by everyone. All of the casino games are theirs to play, no matter lucked base or skill base, as long as they are having fun from it.