Ethical / personal advice needed! Any opinions appreciated!?

I don't really think that it would be disrespectful at all... unless you were to make it that way by talking about it with other people. Or telling her that you masturbate while you think of her. Those are two things you shouldn't do. :) If you don't do that, then I think it's okay to think about her. People are attracted to who they're attracted to for whatever reason. I don't see why ual attraction would be considered disrespectful. :)