My older son sounds a lot like your daughter... He's in to me now for about $7,000 (car repairs, car replacement, computer repairs, wasted college expenses -- he dropped out, etc.) I did finally cut him off. He tells me that he is going to repay me, but I ain't holding my breath.
I have higher hopes for my younger son, but I am less quick to loan him money. So far he has paid back everything I have loaned him -- always a good sign