Why are you afraid when you got the second you in the family, the feminine gender doing what you got addicted and experience in, you don't need to be afraid because you'll definitely be the best gambling trainer of that girl.
It's would be even more better to coach her early the strategies best used to avoid been fully addicted, to maintain portfolio balance and guild her properly. If it takes you to be older to get greater experience, it can take some few months for her to reach your level without passing the roughness you encountered.
Though, you need to recall we are talking about someone who is way younger, by experience the youth can be very stubborn and she may feel she does not need any advice coming from his father, it does not happen only with gambling, it happens with all kinds of things which come and go in life.
In my opinion, it would better if instead of becoming a "trainer" for his daughter Op became rather a figure of control or someone who watches over her, so she will not become addicted to gambling, in my mind it does not look or sound good for a father to be part of the gambling life of his daughter. He may feel guilty in the future if his daughter started to become addicted to gambling or lost an important amount of money.
It would be the typical case of people who regrets encouraging others to gamble because how their friends and family end up.
Well I'm not trying to judge him but for a father to allow his underaged kid to gamble is very wrong even though she's very close to the gambling age but he's supposed to allow her get to the required age before doing that if he could allow that it means he'll likely allow her do other stuffs that's not required of a minor which is very bad. How will he feel is she ends up becoming addicted at that tender age.