I've been through this and it has not ended well so far and I am fully expecting the ticking time bomb to explode so much so that I am looking to buy her life insurance with my sons name on it.
This may sound extreme but I assure you its not.
First starting point, its fairly clear she has an addiction and not just a desire to play cards. Treat this addiction as you would a crack cocaine addict because its at the same level, it needs mental and emotional treatment or it will get worse.
Like any addictions its a waste of energy helping someone who will not admit they have a problem but there are some numbers available online to get her at least talking to someone she may listen to. Some of these pass them on to line help groups, the number of people on these help groups in no doubt staggering.
She will not get better on her own, her brain no longer thinks logically or sensibly in relation to this so it is almost futile to try and have a sensible discussion. At one point she will likely hit rock bottom and agree to get help, its a lie, you'll bail her out and within a few weeks she will be going a bit deeper, this will be rinse and repeat behavior if you allow it.
Your case could be lucky if there is no loss of money involved so maybe it is not entirely family and life losing impact yet but signs are maybe there so you need to act now. Get all house, bank account and other things into a safe place she cannot easily access without a co-signature.
My case went from cards, to football, to lotto to online casinos to stealing from friends, giving away land paper, loan sharks, threats, violence, greedy friends lending for high interest feeding her habit, threats, separation and me trying to get my son safe. Without my son it would have been an easy gtf out of their, that the tough part.
Even having lost everything she will still gamble given half a chance. Leaving a bank card on a table or safely in a drawer is the same as leaving a bag of coke out for a drug addict, they have zero control or logic and lie to themselves so much they have zero chance of telling anyone else the truth.
Let me know if you find a good source for help, rehabs still seem a luxury here and still only designed at those who want to change.