Well, i find something funny the idea of a shipping between Cosmos and Princess Eris just because Eris is Discord’s cousin and Cosmos is Discord’s ex, so… the perfect revenge aganist Discord (for Cosmos’ logic) is dating with his relative, in this case, Princess Eris.
 
But from that plan, actually Cosmos feels she loves Eris because she is like Discord but evil, not so much funny like Discord but her evil is so poweful and then, the feeling are mutual.
 
And Cosmos just stuffed Eris because she wants to avoid potential rival in Eris’ love, turning her “ugly” for the others but beautiful just for Cosmos.