it's a fighting game, hard to have much character development but most of it comes from what you know. From what I know about Vitale, he's basically using her feelings to his advantage. To him, she's expandable, if she dies, he'll jsut pick another performer, if only she knew.
While I loathe Eliza greatlly, her story barely covers what she wants to do or who she is as a character. She simply comes off as a villain who is evil for the sake of being evil and that's boring. Even dio from Jojo is more interesting, even if he is over the top.
SG's a very great game with a loveable lore and world, but sadly, when it comes to character development, there's a massive lackluster. Hence fanfictions coming into play.
Going to be honest, wrote one myself, unlike the anon who wrote the Dahlia story, it's not lewd, sadly.