I suppose many people cannot simply relate to the story of the OP as in many countries the fact that some women like to gamble is not only nothing new but it is incredibly common as well.
And I do not see why this should not be the case as now many women have their own jobs, earn their own money and they can decide to spend it in whatever they want, and if they want to spend their money in having some nice experiences at the casino I do not think there is anyone which should be surprised about it, since that is also a decision many of us take as well.
Women had thrived for equality and they are proving that they are worth it. Women had been excelling in jobs that used to be dominated by men alone. So there shouldn't be a surprise of there arel lots of women who are gambling nowadays. As you stated, they already have the capability to support themselves, often times they even support their husband and family because women do great when they focus on their jobs.
It has been shown by many scientists and research agencies that men are more involved in gambling than women. In the end you have to have a lot of money at your disposal, otherwise you will not get there. And women prefer to focus on other things in life than on gambling. Women are more looking for stability while men often push the boundaries of life. I think that has to do with the amount of testosterone present in the body. Yet here and there you also see some women gambling in a casino. But more for fun than to get rich with it.
Often times research got obsolete. So we shouldn't rely on it 100%. Besides research is just done via samples and does not represent the entirety of the situation especially when it comes to social experiments. There is always a limiting factor that makes it prone to errors and revisions. If you conduct that experiment in my place, you would say the gambling industry is dominated by women because most women in my place are involved in gambling while their husbands are busy working for their family living.