If our characters have never or barely interacted send ✌ and I'll say how I'd think they get along. (Not Accepting!)
This was from centuries ago, sorry that I’m only getting to it now BUT HERE WE GO.
As a Devil Elwine would have a bit more interest in him than she would most other people. Elwine has basic respect for any entity at default, though she will only serve her own. Once she got a look at Ivlis and saw what he was like, however, all that respect would probably fly right out the window.
While she would be pretty disgusted by Satanick’s obsessive attitude towards Ivlis, she wouldn’t be particularly sympathetic towards Ivlis either. He’s supposed to be a Devil which means he should be much more capable of looking out for himself than this, and so she would attribute his lack of ability to fight back as a weakness he created on his own--whether it be a lack of effort or inability it matters little to her.
As an angel I think by default Ivlis would be disgusted by her as well, especially if he were ever able to figure out the....uh. Demented relationship she has with her own God, there might be some jealousy there?
Stars is much, much trickier. Depending on how much Elwine knew of what Stars was, could...or maybe not change things?
If she didn’t know what she was, Elwine probably would completely pass over her. She’d just be a bunny as far as the cat would know which is something she has seen plenty of. A magical bunny at best, which still isn’t anything particularly exciting in her world.
If Elwine DID know what Stars was then that’s different. Stars is a singularly unique creature which means she might provide something new, a distraction, an entertainment, a new reason---something.
I don’t think Elwine would know exactly what she was striving for but she’d just ask a lot of questions. It’s something to do, and Stars has answers she might be willing to give.
No idea how Stars would view Elwine though--ambivalence, I imagine?