Well, you should not have allowed her to be exposed to gambling at such a young age even though there's a chance that she might end up discovering it by herself when she's older but this is better because she would have the mental capacity to handle the pressure that comes with gambling. You can't change what has already happened but you can start guiding her so she won't make mistakes as she gets older
If the father is gambling, it's almost expected that the daughter will at some point see that his father is gambling therefore, she will be curious with it, and will also try it as well.
You've said it that at some point, she will discover it as well, but in a different way and that's true especially now that there are still lots of gambling websites being promoted online, but I don't think it will take too long for her to know gambling just because of how online gambling is being advertised in the PH right now. I agree with what you said that you can't change what's happened, and this is the perfect opportunity for the OP to do his duty as a father. To guide her, and not get addicted to gambling.
And I doubt that she would necessarily get acquainted with gambling. I think that not everyone tries gambling after living their life. Many girls and women from my circle of friends do not even know what "gambling" is and will never find out. They just have a negative attitude towards casinos, and that's all. Therefore, I think that a father should gently explain to his child that he should not gamble, but rather look for another, more predictable hobby.