Have you ever heard the expression of:
Don't dip your pen in the company ink OR
Don't **** where you eat?
Basically it means not to get booty where you work. Yeah, I know that it might be difficult since you already like this girl, but most relationships don't work anyway. Wait until one of you doesn't work there anymore. I've personally learned from experience, I had to work with an ex-, it was very uncomfortable and she was always trying to get me into trouble with our boss (she also happened to be the boss' favorite).