I have a family full of addicts, addictions to a variety of things. The gamblers are the ones that have never been able to stop.
If you're addicted to drugs, alcohol, risk taking, food & exercise additions all are limited by physical ability to partake.
You'd basically have to be in a coma to not be able to gamble these days, it's far far too easy.
The worst one in my family has gambled away more than one home, more than one family (indirectly), lives alone now and this is really all they have left. Still not stopping and in their 70's now.
Not saying ALL gamblers are doomed to lifelong addiction but I do think it's the hardest addiction to quit.
And while she has no real incentive to quit - while you and your parents continue to bail her out - then that makes it even less likely she will.
There's a saying for loved ones of addicts
You didn't cause it
You can't CONTROL it (you've already tried and failed here)
You can't cure it
Only she can and only if she genuinely wants to.
I may get laughed at but there's a book, just a normal novel, called Rachel's holiday by Marian Keyes. It's actually quite light & humorous in parts but it's written from the perspective of the addict protagonist and more importantly it's written BY an addict. Marian Keyes is an alcoholic.
In this book the main character (a drug addict who od's) is basically forced to go into residential rehab by her very concerned, dysfunctional but loving family.
A pp said about GA being full of people "doing" rehab for other people. That's explored in the book, as is denial that they're addicts, their belief that everyone else is viewing them abnormally and unnecessarily judgmentally. But through the main characters own experience and path through rehab inc counselling there's triggers for them realising "actually no that's not normal" "actually I've turned into the very thing/person I was trying to avoid"
Where I find it's useful for those of us who aren't addicts but have loved ones who are, it helps to understand the addicts perspective - but not in such a way as to make out that it's an acceptable way to live, or that addicts should be completely and unconditionally forgiven for what they've put others through (although guilt at that realisation is also explored) which is very clever actually.
And one of the smaller characters is a gambling addict though it's not looked at in great depth.
Supporting the kids - who are completely innocent in this is one thing, but supporting her is not doing her any favours really.
And by her knowing you and her parents won't let the kids suffer you are indirectly supporting her to gamble - she doesn't need to keep money aside for food, clothes, bills etc because she knows you 3 will pay up, that means the money she SHOULD Be putting money aside for essentials she can waste on gambling with no consequences.
To be perfectly honest the best thing would be for the children to move in with you or your parents ASAP. Then she can be truly left to sink or swim and that MIGHT give her the incentive to quit. No guarantees.
It's a horrible situation all round, but that's the reality. 