suncatcher, I run into the same issue with my dad and my sister. I found it best to say my peace, and then just get on with my life, with occasional lapses into anger just for kicks. To say that I've accepted the situation would be an over-exaggeration, but thanks to SR I feel free to spew out the ugliest, rawest emotions out of my system, and handle IRL situations with as much grace as I can muster.
The one thing I said to him, which I really said for my own sake, was, "You will never be able to say that nobody told you that these would be the consequences. Your enabling her now is just merely passing the buck to her daughters years down the road. Do you honestly feel that doing XYZ will help her get back on her feet, or are you doing it to make YOURSELF feel less guilty?"
He couldn't really say anything after that.