So i was spit balling around with the idea of demons of envy and i settled on a centaur look and i kinda dig how both girls came out, the animal half is a general four legged animal, decided to go for something ambiguous.

Envy is a very petty thing in general which is shown here, one girl wants to be fat and one girl wants to be thin.
thinking about it more Envy is like the joke circle of hell, anything that can be jealous will.