Unfortunately, we cannot assess how many female gamblers out there are gambling online as it is one of the great things about it which is anonymity where no one will know who you are other than the gambling platform if they require KYC. Anyways, I'll disagree with your opinion that only a few women are gambling in physical casinos as I've only different casinos and I always see a lot of females around me. They may not be as many as the males but there are a lot of them out there gambling.
Yep, It's nearly impossible to asses how many female gamblers are playing online and it is the same as men unless we submitted KYC and intentionally say what gender you may be. I guess it's normal in the casino that you are playing that there are females around, That's nice because I guess it helps other gamblers to stay focus since it's normal there and not so many men is eager to be in the same table of a female.
But we can assume that there are lots of female now a day playing in an online Casino due to the availability of the game in mobile devices. So it can be access anywhere, anytime. Just like there are many female engaging gambling activities in physical casino, I believe there is more who are playing in an online casino since those who are shy to go out and play in a physical casino can just stay at home and play in an online platform.
Did you watch her play and see how her bets turned out? As they say, there is a woman for every man, and it would be unfair if there were no women who gambled, but from what I've seen in movies, ladies always have one or two objectives in casino houses rather than playing in the casino itself.
Movies that is not a documentary or true to life stories are all fictional. It is all in play according to the writers belief and imagination so better think twice before believing in them.

I can't say there are no women who gamble as we only have a few physical casinos here, but there are women who are sports fans, they go to viewing centers where men and adults watch the ball and make a seat for themselves to enjoy the entertainment of football, and they also bet on their favorite sports.
The fact has been established that even women loves gambling. It was established in the ancient time, even the Roman Empire establish a holiday that women can participate in gambling events during those time of holiday.
I can answer your question since I've defined the contexts from which I'm coming from. Ladies are not seen as gamblers; perhaps internet casinos that do KYC might justify the response better, but you will rarely find women in general who like gambling.
They gamble when they chooses a husband and being gambled when their parent chooses their partner.

After all gambling isn't limited for men only.