If you happen to find yourself in a religion that say gambling is a sin and could end up being ostracized then it's in your best interest to either be obedient and keep to the laws of your religion or you could change to another religion where you would not be criticised, left for me inthink why most religions comsider it a sin is because they feel it promotes greed and other illegal activities, however it would be very bias when the say it's a sin but only discriminate or punish women only because that would be promoting gender inequality.
Anyways the ratio of men that ate gamblers would always be greater than women due to factors like religion, gender inequality, fear of discrimination an so forth, also men in our society you'll find men more interested in things related with gambling, like sports, video games, and other events and since most don't have an idea about it, they see no reasons to pick interest in it as well, hopefully in future more women could likely begin to pick interest in it because of the introduction of women to various sporting activities.
So this difference have made a limitation to women's involvement in gambling and this differs from country to country and region to region and all the same with the coming of online gambling, the number of female gambling has increased and more also it is a fact that there can now gamble in privacy which is more inclusive in the region where gambling may be prohibited or banned.
In my country today, gambling in some regions is prohibited but the Sharia/Islamic laws that prohibit gambling also have several other laws that set limits as to women's involvement in public affairs, and these limits have affected both women and men in many ways which have pause a limitation to the general public involvement I gambling.
But if you as me to make a ratio as to the rate of women vs men give men 80% and women 20% from the total of 100% so this is a pointer to what I mean when I said that the male. rate triple women's involvement in gambling.
Today's women are independent, working, and sharing family duties. Isnt it better to include this? Could their gambling be influenced by social acceptance, education, or risk tolerance?
Regional and cultural factors also matter. But responsibilities change. As you said, female online gamblers are rising. However, increased access may explain it. Consider that your 80:20 % may change depending on a region's location and culture.