Ingrid Just push what your daughter said to the back of your mind and get on with life. She is depressed, being married to a unemployed compulsive gambler must be a difficult and depressing life. Where does he get the money from to gamble? Despite what one poster said, living that way, with no money, probably debts and all her hard earned money going on whatever he gambles on would almost definitely cause depression, even if she had previousy had the most resilient of natures.
If we are going to bandy around psychological terms, your daughter and her DH seemed to be locked into a relationship of co-dependency. Until she can break that bond and separate herself mentally from her spouse and look for solutions to her problems, there is nothing much you can do and unjustified abuse like this is par with the course.
However, you are in charge of how you respond to it, you can collude with it, put on metaphorical sackcloth and ashes and join your daughters codependency, or you can see it for what it is - the flaying around of a woman in an impossible situation trying to find a way out that doesn't involve facing up to the real facts of the situation. It could just be that this is her first step on the road to reality.
However, if the help you give her/them includes paying debts or filling gaps in their expenditure like buying food or clothes. I would stop doing that now. While you do that you are colluding with them and making it easier to avoid facing up to the facts. You may need to be cruel to be kind and let debt overwhelm them, because only then will they face up to the real situation.