Which vampires Bella would be attracted (physically or emotionally) to of Edward didn't exist based on her book thoughts? Who do you think she would want a relationship with if no one had a mate?
Looks-wise, she seems to ranks Rosalie and Carlisle up there with Edward. The others are attractive but her descriptions of them tends to focus on other things (Esme's softness, Alice's grace, Emmett's muscles, Jasper's scars) rather than the just jaw-dropping WOW we get about Edward, Rosalie and Carlisle.
Personality wise, Bella seems to love Alice and Emmett.
The thing is, though, I almost think she'd find relationships with them kind of boring? That is, the fact that Edward is obsessed with her is part of the attraction? He's fighting his very basest vampire instincts not to kill her, he's putting up with incredible temptation and pain to be near her. It's literal proof of his love for her and I think that's very intoxicating and also just, like, reassuring to her.
Carlisle's not bothered by human blood anymore, either Bella's specifically or anyone's generally. There's not much danger, no real tension, no proof. He wouldn't be struggling. Emmett and Alice would just be like, "sure I'll make you a vampire or, um, maybe ask Carlisle to do it so I don't kill you" and wouldn't brood about dooming her to a vampire life and again it would loose some of that intensity and romance, that "I love you so much I can't condemn you to this!" thing.
Jasper would probably just kill her, whoops, and Esme seems firmly in "mom" territory in Bella's mind.
Rosalie? Maybe. The problem is convincing me that Rosalie would like Bella back. Fanfic writers can do it, but in canon one of the things I love most about Rosalie is that she doesn't like Bella. Universally adored main characters are annoying to me. Some people just don't vibe with others and that's okay! She is the most Edwardian in her dramatics and anti-vampire stance. But again, the thirst is not a specific problem unless you re-write it.
Outside of the Cullens, maybe a Volturi? That has danger and has the moral stakes (although they don't end up meaning anything in Breaking Dawn) AND had the Cinderella sort of fantasy of this rich, powerful, borderline royal vampire. Marcus is young and if Bella could catch his attention there's that "proof" and reassurance again, like this guy has been an empty husk for centuries but he sees something in her, wow!
And I don't mean to like, crap on Bella here. This is a romance! The whole "I am singularly special to this person" is part of the fantasy. And Bella as a character with her self-esteem and abandonment issues is extra primed for it.
Not a vampire, but there's also Jacob, of course. She finds him physically attractive, they are emotionally close. She is, what, a year or two older than him though. I think in a world with no Edward they might date but the first go-round wouldn't last too long. They're too young and don't have the unchanging vampire factor or imprinting. I think if they're both still in the La Push/Forks area and single at the same time in the future though it might work out. Imprinting is a problem but again, there's that risk and also the thought of like, "he could wait for true cosmic love but he picked ME instead."