If the person is not willing to admit that there's already a problem with how they manage their gambling activities, expect that there
are worse things to happen, that person needs more attentions to make them realize.
I'm following your point in which the problem will continue and it goes deeper if the person will not address the issue much sooner.
Trying to keep in touch and always reminds the person may give them some hint that their addiction is no longer controllable
and there's already a need to seek for professionals.
That's right, such people should always have someone by their side who can divert their mind whenever they want to gamble and that one person can be a best friend, a spouse, a sibling, or even a parent. The person who is addicted will surely not be able to control the urge themselves but if there is someone available with them to accompany them, that might change their mind.
You can't take an addict out of their addiction simply by saying that they shouldn't do what they are addicted to, but you will need to find ways that can divert their mind and engages them in something else and that might help them gain some control.