The greatest fear of this action is, "what if this girl becomes addicted? " Just what if? Then it's going to become a big problem for the girl in the future which she might exhibit some addictive behaviors that no man would want to risk getting married to an addict or even after the is married, what happens when she starts using her kids money to fulfill her gambling needs, that means her children will suffer it too. If you must let your kid gamble, it should be at the right age and also with a strict guidelines of not becoming addicted.
The fear of the addiction is mostly the main issue around all of this because it usually start off as an innocent way of having fun and getting some money from it but then it later happens that things change and the unexpected happens you then have to start guarding and putting her back in oder from the addiction she may be suffering. Obviously when it's time for marriage that aspect of her will not be revealed easily because they know how detrimental it could be.