I wouldn't say she's playing favorites. Normally, it would be 50 years of domination for humans then for demons in alternance. Basically, she's the parent who told "you can play video games today and your brother plays tomorrow" (instead of being a good parent and tell her children to play together).Just call her a bitch that playing favorites.
But now the humans have decided that it's still their turn to play games and summoned another Hero.
The interesting part will be to see if the Goddess actually intervenes and punishes humans for breaking the rules or not.