If you really want to help someone with their addiction, first you need to identify the problem, to begin with. Oftentimes any form of betting can be seen as terrible but it's important to note that it only becomes a problem once a person starts involving their emotions and health into it instead of just their wallet. With the right perspective betting from your own wallet can have positive effects like its social aspect of making friends or the improvement of your risk/money management skills.
People often like to associate gambling with thugs, gangsters, or in general, label it as an overall sin, which is simply not true. Gambling is a celebrated tradition in many cultures and an extremely thrilling hobby at that. The truth is, excessive amounts of anything can have devastating effects on your overall being, and gambling is no exception.
To understand anything you need to think of the opposite point of view and work backwards. Think of healthy things like vitamin tablets for example. A widely popular medicine, full of good stuff recommended by doctors. Considered healthy and great for you in general but even these tables have a recommended amount on display. Eat too many and you're in for a bad time for sure.
If you truly want to help someone you need to understand things from their perspective. The main point that needs to be established is that gambling is like anything else in the world. Good risk-management skills could help you improve your life just as bad gambling addiction could ruin it.
A big sign of addiction is secrecy. There is nothing wrong with gambling as long as it's for entertainment purposes and money only. Once a person starts hiding their habits it becomes a problem. Hiding your life away from your friends and family isn't a healthy approach and indicates addiction.
Make sure to involve as many people as possible during gambling sessions to ensure it won't spiral out of control. It's much harder for a person to fall for addiction with people around that give them a reality check. For example, you can form a group of friends and play online slots during holidays together, to ease people involved into the process, or in general make it a group activity that's fun and entertaining for everyone.
"Rome wasn't built in a day" - John Heywood
Just like Rome, deeply embedded habits cannot be changed in a day. Every long routine, habit, tendency, pattern, or style needs time to be developed or in this case, 'undeveloped'. Whoever you're trying to help, their addiction has probably been deeply inrooted in their life.
To have a healthy transition you have to compromise. Don't try and take part of their life out completely right away. This will only make the change feel worse and leave the person feel indifferent to you. Try and implement small changes gradually like limiting their time playing per week, then per day, and eventually all back to normal.