Yeah no. If it's gambling addiction then so is a mall shopping spree because they have signs with blinking lights and other positive reinforcement including sales people who will be disappointed if you don't buy after their pitch.

People hide problems of responsibility behind technological wizardry claims. Yeah there are big problems with abusive psychology under capitalism. Yes some of them have been refined a bit and are newer but this isn't gambling. Gambling you stand to win back money if you succeed and there's the thrill of blind results driving people to keep pulling the lever in expectation of the excitement of the unknown and the prospects of that. We can talk about children with a lack of impulse control being preyed on by lootbox mechanics because they're kids but adults need to have this kind of basic skill to survive under capitalism. That skill being a modicum of self-control. But this is knowing exactly what she was purchasing and how much it could come out to.

I agree it's a sign of some sort of mental unwellness but I'm not sure it's something diagnose-able with a DSM code and in that sense it could be quite hard to treat with therapy as it would likely involve really confronting their inner self, who they are, formative history, etc which are things many people find hard and would rather avoid. If they're already avoiding the not that hard work of financial discipline then short of something seriously challenging to their life forcing them to confront themselves they may not have it within them to face the hardship of this kind of self-investigation and course of change. Maybe the threat to their marriage will do that but often it takes a bigger jolt than that and often such a jolt of sufficient level isn't reached at all and the person goes through life with constant crises and no real healing. I hope for OP's sake and that of their partner they are able to get at root causes and find some healing but I hope OP is realistic about this being a common problem that may not end well either.

As far as dopamine response that's why I brought in sex "addiction" and porn "addiction". There are cases in the literature of people who will compulsively masturbate to the detriment of their well-being, who will shirk jobs, responsibilities, a social life to sit home and just pleasure themselves. Masturbation however is not an addiction nor an abusive behavior and their problem does not stem from masturbation or incredible sex toys but from motivation, self-discipline, etc. Often people with ADHD or other problems with long-term goal-setting and thinking have problems in the nature of that type of thing of self-destructive short-term thinking behavior that neglects longer-term goals. But the solution isn't to say "oh it's an addiction, not your fault" but to understand it is their fault, they need to find ways to cope, to discipline themselves, to avoid triggering things, and to survive and thrive in the world they find themselves in by adapting.

Abusive psychology under capitalism is a plague and ruins a lot of things and lives but it is not an addiction and doesn't stem from addiction and compulsive behaviors are not addictions and should not be regarded or treated as such because it's missing the real problem on a personal level (yes, yes capitalism is the REAL problem but OP can't do anything about that).