If you really want to score this chick in the bag you must rattle her cage a bit. It honestly seems like she like you as a friend but needs a little extra attention so she flirts with you at work. You would also come in handy for the occasional favor if she needed one( which you just did) being that your such a "nice guy".
Now what you wanna do is tell her the night before over the phone that your not gonna be ableto pick her up for this interview. "Something came up, but I can give you a ride home if you like" that's wen you ask her out for drinks to " celebrate" new jobs.
Also if your focus is "what not to do" that's a sure way to fuck up
I wont write you a step by step manual on what to do; it doesnt seem like your ready for this type of thing anyway. Just have fun and learn from it.
Easy