Aurora Winter:
Aurora I think would enjoy Distracted Heart by maritumix, it's a neat song and I think it would be calming to her. She'd also probably like Although the Sky by Dorkus64, because she's a very cheerful girl with nothing wrong with her. The fact that this song is one of a few that can make me cry is unrelated.
NEBULA:
NEBULA is exclusively processing the most overwhelming soundscapes to keep her emotions regulated slash to feel something. For that, guarantee it's something like Dream Drive Operating System by GHOST DATA or WYSI (When You See It) by Camellia.
STARGAZER:
STARGAZER I think would listen to music I can only really describe as "weird", but the kind of weird where you kinda get it when you listen to it. I'd suggest something like Nisemono or of Ambrosia, both by Frums. It is, notably, still overwhelming, at least from a perspective of me trying to estimate a normal person's sound preferences, about on the level of DDOS back in NEBULA's systems, but I think STARGAZER would veer towards "overwhelming through detail overload" as opposed to NEBULA's "overwhelming through just being plain loud".