It looks like she sees you guys as friends, she probably has a thing or she probably doesn't. You can directly ask her that only if you know for 100% that she's interested in you for certain (or you wouldn't write it in here)
You've mentioned you've had some laughs over drinks and outing; were you cocky and funny? Did you flirt? Odds are that you didn't cause you said you started off professionally.
The best way to know if a girl is interested in you is by kino check and body language, try and get into her comfort zone and when you know you're in it, go kiss her!

It can be invariably awkward if you were too formal a gentleman for the escalation.
A kiss can work without kino and escalation (like they picture it in the movies

) only if there's a downright mutual attraction.
The only thing you could do now is to gradually start teasing her on her job subject, act a little cocky, have fun, pat her on the back when you compliment her (don't compliment her too often - its ok for once/twice) let your arms brush, bump her on her shoulders when she says something and you didn't find it funny, put your arms around her shoulders for a few seconds and see if she objects or stays stiff (if not, then you know you can proceed with a dragged kino)... Chances are that she'd pat/touch you on the back to show you something or like that.
Well, the above is just an depiction on how it would work very naturally. When you still see a lot of IOIs coming it means she likes you
Beware: If she liked you and you were too much of a Goody Goody guy who's scared to death to touch her, strong chances are that she'll LJBF you!