@Background Pony #A2E0
When you put it that way, I see your point.

@Brony kaiju soldier
Well they are both humans now. The difference, the less obvious one anyway, being that one of them became and stayed a human of their own free will while the other was forcibly banished and trapped as one.
You can see where the animosity would come from, especially when she gets stuck with a body like that while her rival gets one like THAT. Of course we don’t mind her itty bitties, but Adagio is a proud siren that considers herself the baddest thing around, so it can be irksome when Sunset can simply pull those out and shakes them around to shut her down now.
Don’t worry about her too much though, the attitude is mostly exaggerated to take the attention away from how rock hard her tiny nipples are.

@Background Pony #A2E0
Well, let’s not forget Sunset’s also from Equestria.

Everyone’s got something to contribute, Dagi.

Breasts are just one part of your appeal, Dagi. You’re more than just your cup size.

No wonder Adagio hates humans so much…

Envious*

Yuup this seems intresting.

Poor little fish is out of her depth against the land mammal. That’s a tough break.

She has no need to be jealous, her cute chest is better anyway