She most likely has no idea that you're interested.

I can say from experience that generally the workplace is not the best setting in which to find girls to hook up with. My job is all UW students so there's tons of money girls there. Once I realized that they were just being friendly and weren't indicating that they wanted to have sex with me I started having a lot more fun at that job.

Besides you can usually get away with more crap with a chick that's your friend than a chick you're trying to hook up with. Plus having chick friends means that when you go out with them you get to meet their hot friends and they think you're safe because their friend seems to like you.