Gamblers at their teenage, do many mistakes. But it doesn't mean they are bad. Actually sociaty always treated gamblers as suspicious and so was happen with your newbie. She wasn't sure her momey was stolen or not but suspicious mind force her to believe such thing. actually when it comes to gamblers, people are too quick to judge them without trying to reveal the trusth. Let gamblers have some time figure it out. My perception about them is that, your nephew would grow up soon with hard experience and then he'll set his mind to figure out which is good and bad for him. Until that, give him just one advice is to control himself during gambling, only stake what he can afford as he also said already
Not all the gamblers are the teenagers,with my experience most of the population of the gamblers are from the 40+ age category of gamblers.After the stress from their job at the work,the most seeking entertainment will be the gambling.The gambling is like the drug to satisfy at their 40+ ages,So they will gamble with the money from all their expenses.Most of the experienced gamblers will choose the free money after their spending to their food and their family medical expenses.Because the medical expenses is not the permanent one,the medical free months money can be used by the gamblers on gambling.