Personally:

It's not the thinking that is a crime, it's the action itself. You shouln't feel bad for finding a girl attractive, that's part of the human nature, if you would do a move, that's all another story.
1) I'd say that you should try to limit your contacts with this girl as much as possible in order to not torture yourself and to leave no space for temptation.
2) everytime you feel the tease, keep in mind that you'd just throw your life away and that the relation with the girl couldn't last because she wants way different things than you in life and that a knock out the cherry game doesn't worth losing job (possibly) and the one who really loves you.