"But that's not possible unless she becomes like the rest of the world, slutty, and so on."
No. The world, although it has some terribly shit people, an awful society for the most part, the world itself isn't inherently bad. It's not a corrupting force.
If she were real, she could be in this world, assuming she's a person, that is. You and her would realistically go out and do stuff. You'd figure something out, you'd both be out doing awesome stuff with each other.
If you were 2D... dimensions don't matter. Your question is would she be with you in your existence, or would you be with her in hers. I don't like having to say this, but either way it doesn't matter, since both happenings are near impossible. If by some improbability you end up together, no matter where it is, you have to have faith in yourself you'd pull through. If you don't have that, you've nothing but despair.
I admit I get what you mean though. If she were to go to you, you'd strip her of her friends, her family, everything she knows and cares for. I know precisely that feeling. The only answer to that is for you to be with her in her world, I suppose. Still have to believe that you'd do the right thing and sort everything out.