True but one of her fatal flaws is probably her obsession with humans/mortals. At one point she probably did like Sinbad but Maria changed him for, in Eris's mind, the worst. Your right about playing games, I don't think she gets any satisfaction from crushing others. You also have to remember she gave her word 'as a goddess' to Sinbad. While they don't go into detail about it, she isn't aloud to break that promise. Implying that there could be a number of rules deities from that universe have to follow.